Like I said in a previous post, I know I'm wrong based on the mechanics.
IMO, the odds are so overwhelmingly in favor of something like this happening as compared to the uncontested runner missing home that it deserves some critical thought as to where the priorities are given.

No sarcasm intended here.
But are you and others in opposition to my viewpoint suggesting we blindly follow the letter of the law re: mechanics with no exceptions while also saying it's ok to fudge a bit on rules if it's the 'expected call'?

I'm not suggesting the mechanics be rewritten. I think it would be impossible to do so in a comprehensible fashion. What I am saying is there is room for exceptions.

Umm, yes, teams do do that. I have coached at the high school level before and every game I assigned my bench players certain duties. A couple would keep charts, a couple more would watch the opposing coaches to try to pick up any signs they were using and yes, another couple would be watching for missed bags, tag-ups and if the umpires were also watching.

And as far as no one else in the park will see that touch of home, my catcher damn well better see it. He has nothing else to do at home with the bases loaded and the play going to first.

No. With respect to that part of the issue, what you did was correct, and what BU did was awful. While you shouldn't have been looking at what you were looking at (and a good BU would know that you weren't looking, and probably wouldn't come to you anyway), the fact that you were let you give information when asked. You should definitely do no more than that. There are calls that belong to multiple umpires (OBS, INT primarily), but pulled foot is not one of them. You should NOT overrule anyone on this type of play. OTOH, your moron partner A) shouldn't have asked you and B) should have changed his call after he DID ask you.

I don't need a clinic re: this issue. I know the mechanic and I know I'm arguing against it. I've said so in two other posts.

Why is it that some rules can be compromised with virtually universal approval and yet a mechanic cannot?

The odds of R3 missing the plate in this situation and being seen by a defensive player and being appealed is extremely miniscual.
The likelihood of BU asking PU for help at first, not so unlikely, in fact not even considered out of the ordinary.
So if you're playing the odds, where should you're eyes be to most likely avoid the proverbial SH**storm.
Let me finnish with this.

If, as in this case, F3 misses the bag, how many people, players, coaches, spectators and evaluators saw it? I'd say at minimum, 1st base coach, everyone in 3rd base dugout, most spectators on 3rd base side, pitcher, catcher and PU if he was looking.
If PU doesn't see this there's a whole lot of people wondering how this crew missed such an obvious call.
If, same situation R3 misses home, how many people see it?
I'd say, if any, 1.
Which of the two calls do you want to get right?

I'm not saying no one was assigned, though highly unlikely in most cases.
What I'm saying is these are 16,17,18 year old kids, bottom of 7th, bases loaded game winning out possibly being made at first, how many of these kids have the discipline to be watching home instead of their attention being diverted to first in this situation.
Like I said before, the reality of this situation is no one will even see a miss.

A good crew with a good pregame will probably have a sign that tells their partner they have something.
Nothing worse than one ump having a correct call and the other never coming to him for fear of hanging him out as well.
If you get the sign then at least you know you have the option of going to your partner.

While I agree that a good BU should have made the correct call himself, without having to ask for help, I disagree in that I feel the PU should have been watching for the touches of 3rd and home, as well as the pulled foot/swipe tag at 1st. All it takes is to glance at touches, it doesn't require a stare-down with the runners.

When there is a 1st to 3rd situation with R1 and R3, for example, I move up the line toward third, glance back to see R3's touch of home, and continue on my way to cover R1 coming into 3rd. I don't need to stay home and wait for R3's touch. I am able to perform several tasks at once.

I think the same thing applies here. The PU can see R2 touch 3rd, R3 touch home, and still follow the ball to its destination.

This is what the Official Rules Of Baseball says in its charge to umpires:

"Keep your eye everlastingly on the ball while it is in play. It is more vital to know just where a fly ball fell, or a thrown ball finished up, than whether or not a runner missed a base."

It goes on to say:

"If you are sure you got the play correctly, do not be stampeded by players' appeals to "ask the other man." If not sure, ask one of your associates. Do not carry this to extremes, be alert and get your own plays. But remember! The first requisite is to get decisions correctly. If in doubt don't hesitsate to consult your associate. Umpire dignity is important but never important as "being right.""

Never. If he asks I tell him what I saw and it's his decision to change or not. But if I tell him I saw something different than he called and he don't get it right we will have that post game discussion I mentioned earlier because I don't understand why he asked for help and then did not use the information.

Here's where I am on this: of course I agree that PU should be able to glance at the runners touch 3B and/or the plate without difficulty, and probably still see the foot at 1B. In this case, sure, if you see a pulled foot/whatever you give BU what you saw. But its still his call.

What I completely disagree with is your expectation/insistence that the PU prioritize his 'piggyback' of the 1B call over the touches at 3B and home. Its similiar to PU coming up to take the play on the lead runner at 3B in a R1-only situation: PU helps there if he can, but if he has to stay on the line to make a fair/foul call, then that's tough luck for the BU, the BU has to take that call.

Because the fair/foul call is the PU's priority. Just like the touch of 3B and HP is here.

It's amazing how good ol' common sense can get you thru most baseball situations.
Some of you should try it.