So, was the second bridge installed in 2289 as the first paragraph in that section states, or at the same time as the 2287 refit? This seems confusing the way you flip-flop on the date. Or are you saying that after only 3 years in operation she had a 2 year of refit?
It's not uncommon for new vessels to go through minor refits at the beginning of there service lives as new technologies become available and are released fron there testing stages. As for the Excelsior, after being fitted with "conventional" warp drive engines, the control interfaces would need to be changed out to accomodate this, and in the case of Starfleet ships where "bridge modules" can be swapped out the little effort, this could be done several times during the service life of the vessel.