Well to be fair, I agree as far as ST:III goes, with what's supposed to be Spock's quarters an all. But in ST:TMP V'ger was scanning the library computer and so it's reasonable to assume that "Historical data" like the TOS era Constitution would be among the files scanned. Besides, at that time most ships would presumably still be in their more or less "original" configurations, so the data would not be that dated?
As for the starship classes from the tech manual go, I'll meet ya half way. while showing them in their TOS era configurations is an anachronism, which we can ignore, the fact that ships like these exist in the trekverse should be considered established, albeit they should have been shown in their "uprated" configurations.