I assume that's a rhetorical question, btdt. If not, what do you tell him when he claims that was a strike the last inning, or that was interference yesterday or that wasn't a balk last week?

This is not a major problem. Coaches whine. I've learned to expect it and live with it. If they eventually prove that they are too dumb to know when to stop, they get to whine from the parking lot.

For the sake of consistency I have to say something.
This forum is chock full of posts referring to other umpires and smittys that make bad interps, have bad game management skills or generally make incorrect or bad decisions and the folks on this forum are always complaining that "they" have to clean up the mess after such bad umpiring has left the wrong impression with coaches and or players. The general concenus is always that it would be nice if that didn't happen so there would be no mess to clean. This sitch is no different
I agree that in the whole scheme of things this isn't a big deal, but very little on the board is, in the whole scheme of things, however, the sitch btdt is referiing to is bad mechanics, it's not teaching the younger umpire proper responsibility, (which may encourage him to pass the buck on another ump as well) and definitely giving the coach the impression that BU makes that call(which may or may not cause a brief discussion with another crew at another time)
Frankly I'm surprised that more people haven't chimed in on this.
In this type of situation:
Can an umpire ever take another umps call, without permission, and be justified?

If after a conference, your partner went directly to the offended coach made your call and managed the resulting situation with the coach without your permission, how would you react?

Co ump,

If it will make you happy, the (ONE TIME experience) that happened to me is NOT the recommended way to handle this situation.

As a veteran, I would be offended if my partner did this to me. As a rookie, I might not know better and may or may not appreciate it.

Given the situation, where both officials fully understand recommended mechanics and their agreed upon pre-game discussion, my conversation would have been, "PU, that is your call and you have to make it." Then I would support what my partner announced.

Again, it would be great if everything that happen on the ball field could just be handled like the manual. It is just not way.

Hopefully this answers you question.

If you'll read the posts you'll see that the questions posed by the OP were answered by several of us prior to the current diversion.