Re: The Constellation's registry number
You are mixing "obsolete" as in "no longer in use" with "over-writing" or "re-writing" as in "a new story alters the previous story's details". "Starship class" is obsolete in the Trek story simply because the TMP Enterprise, aka "Enterprise Class", was upgraded from it after TOS. The TUC Enterprise is a different ship from the destroyed TWOK Enterprise and it's a "Constitution Class". The 24th century stories refer to the Enterprise as "Constitution Class" based likely on it's final form. Just like most 24th century stories refer to Captain Kirk and omit his time as Admiral Kirk. There is no "over-writing" involved here.
Beautiful summary in a nutshell.
@ Nerys Myk
"The first duty of every Starfleet officer is to the truth" Jean-Luc Picard
"We can't solve problems by using the same kind of thinking we used when we created them." Albert Einstein