Not sure if anybody has brought it up in the thread already (though I'd be surprised if it hasn't been), but the other thing to consider is that in STIV the new Enterprise
is seen with a moderately updated version of the TMP bridge design, whereas in STV and STVI it uses a new module. It seems plausible to me, if Ent-A
really was Yorktown
in a previous life, then the final scene of STIV must see it in effectively its former glory.
We might further theorize that the hiccups and issues Scotty faces in STV come out of a little 'pet project' of getting it refitted up to a newer Starfleet spec (the Excelsior spec?). So we've got a new bridge module, new corridor fittings, new duotronics, all transplanted over the top of an existing framework, and no doubt creating clashes and incompatabilities everywhere. Not as extensive a refit as was carried out in 2271, and it could explain why the Enterprise
is clearly not 'service ready' in that movie. The team put in charge of the refit has had to reverse-engineer everything to try and solve some of the incompatability issues with the old hardware, and the call to duty comes before Scotty can put it all back together again!