Not according to the coach.

Play:

Runner on 2B, batter hits a slow roller towards F4, BU moves in from C slot, watches
catch, throw to F3. (BU is behind pitching area, more towards 1B than 3B)
Runner on 2B upon seeing throw to 1B, heads for 3B. SS fakes a catch and
tag on runner, she reacts, gets thrown out on close play at 3B where PU is
and on the play. Calls time and awards runner 3B. (OBS) Defensive coach
goes immediately to BU wanting him to change the call, saying that it
was not PU's call, he knows cause he is also an umpire and all throws in the
infield are BU's. Coach was eventually tossed for language unbefitting of a
coach/umpire. :)

Well, not necessarily. The first play in the infield is the BU's, but that is irrelevant to the discussion.

An OBS call is the responsibility of all umpires on the field. The coach/umpire is wrong.

If known, the association for which the coach umpires should be sent a letter noting two issues:

1. Unacceptable conduct on the field, and
2. Lack of knowledge as it pertains to the mechanics
of the game. Recommend attending a school.

By every set of two man mechanics I work (ASA, NCAA, and NFHS), the call at third which is the second play in the infield belongs to the plate umpire. Mistake number 1 by our (baseball, I bet, where plate umpire almost never leaves the plate area) umpire/coach.

Then, as Mike notes, obstruction is to be called by any umpire who sees it. Mistake number 2.

He should have been happy his shortstop wasn't ejected for the fake tag resulting in the reaction by the runner. I'm betting mistake number 3, and the reason he argued to the point of ejection, is that he taught the shortstop to make the fake tag, because his (baseball) umpire knowledge made him think no one was watching that happen (base ump is watching the play develop at first, of course).

Baseball umpire's almost never leave the plate area in the 2-man system?

Coach, I'll make you a deal; You don't come out here and tell me about umpire mechanics and I won't come into your dugout and tell you when to bunt or steal!

Baseball umpires will leave the plate in pretty much the exact same situations as when softball umpires do.

But, back to the softball topic...

From the original post: Runner on second, umpire in "C", batter hits slow roller to F4. From the description, it sounds as if the BU moved into the diamond on this hit (behind the pitching area).

Isn't that a violation of the "inside-outside" theory. Shouldn't the BU stay outside the diamond on a ball hit on the infield, and only come inside on balls hit to the outfield?

Not necessarily. The "C" is a long way from 1B. If the BU can move toward 1B to make the call, s/he should. However, you better damn well pray that F4 doesn't decide to go somewhere else beside 1B on the play. Because of that possibility, the BU should not cross the direct line between F4 and 3B until F4 has released the ball toward 1B.

On this play, BU watched, saw that throw going to 1B moved in for good look,
and while watching to be sure of catch, touch of base, did not see the OBS
(fake tag), he could not have made the call. I know, I was BU.

Also, really not suprising, found out that coach is an umpire, LL.

1) Better yet if time allows, BU read the batted ball and be past the F4 to F6/3rd line before the catch, but not to the F4-F2 line.

2) The "inside-outside" theory usually means being on the opposite side of the "base line" from the ball. Once the ball is hit to F4 when in C, as IM said, the BU would be farther away than needed by staying outside the "base line".

That sounds good, but if you think about it, if F4 does decide to go to 3B with the throw, that is the BU's call and s/he would be moving away from position and possibly in the way of a throwback to 1B.

I guess a lot would depend on where the BU actually started in relation to the defensive set-up and the timing of R1 advancing to 3B.

Right of course, but if the throw goes to 3rd, it would be coming from inside the 2nd-3rd line, so I would rather be inside and facing instead of moving parallel to the runner on the outside. That's bad enough on steals of 3rd.

hhhhhmmmmm
 

Inside outside: BU starts on the outside of the defensive players, and after watching the ball, the BU moves inside to make the call.
Two man crew responsibilies: single runner,the BU takes that runner around to third, then the PU takes the runner if she runs for home.
Two or more runners, the BU takes the lead runner to second, and if the runner goes for third, she becomes the PU's responsibility as the BU settles into a position to cover the other bases, and if needed, come to home and cover for the PU who is up the line at third.
Obstruction is the responsibility of all umpires on the field.
BU's, let the ball take you into the play. Important here is to watch the ball and let it tell you where the play is going. Do not over commit, but move easily into the proper position.

Re: hhhhhmmmmm
 

hhhhhmmmmmmm......?

Sort of what I was thinking.

Re: hhhhhmmmmm
 

Except that most of us have the BU take the first play in the infield, even at 3rd.
I agree that "watch the ball and let it tell you where the play is going." is the point.

I believe that
 

that's a bad mechanic. You expose your backside to the other bases and any potential situations, and you can force your PU away from home without any coverage. From my experience. I don't care how young you are, or how athletic you are, or how good you (universal you, not you personally)believe yourself to be, you cannot cover three bases. I've had the pleasure of officiating this game for many years, and I've found this mechanic to be the best.
Again, not an attack on you personally.