Perhaps the registry was to be carried over...
And that would be fine... if the Excelsior didn't already have a ridiculously high number (thanks to the number on the Nebula model).
I was never really comfortable with a lot of the TNG era Excelsior numbers, to be honest, as very few of them ever actually fell within the 2xxx range. If they're intended to represent some sort of chronological number of the ship being built or commissioned, they just seem way off.
I was not comfortable with that either. At the beginning of TNG, it seemed that, while still in use, the Excelsior class was just an old out-of-date class that was more often than not just couriers; rendesvousing with the Enterprise-D to drop off or pick up VIPs. The first few Excelsiors we saw had four-digit 2XXX registries (even the Hood in EaF), and they never got up to more than a 1XXXX registry number even though that's pretty high. Then along comes Deep Space Nine and now we have old Excelsiors and Mirandas with registries of 3XXXX and 4XXXX. And a LOT of them.
This is why I no longer believe that registries are chronological. Okuda himself entertained the notion that the numbers are in fact "batch" numbers, meant to represent a certain batch of ship construction numbers rather than a chronological scheme based on time of production. That's how we can explain that the more-advanced Ambassador Class has lower numbers than the majority of the Excelsior classes; "batch 2XXXX" actually came after "Batch "4XXXX." This actually makes more sense to me.