I'm aware. BIP39 requires the wordlist to check validity of a mnemonic phrase, which is one of many reasons why some people dislike BIP39. This can be viewed as a self-inconsistency of BIP39 spec, however I just think the fact that "wordlist flexibility" of BIP39 doesn't really work is not very important. Official English wordlist can work well, that's enough. In my opinion, the attempts to takeover BIP39 will only make the situation even worse, that the user (even machine) can't tell exact type of those 12 words at hand.
people dislike BIP39 but "checking validity" is not one of them. there are lots of issues with this proposal that has made it not-desirable. for example the mnemonic doesn't give you any indication of the derivation path or the script types and since each wallet uses its own thing, recovery using mnemonic (which was supposed to be easy) becomes hard.
the word-lists and their inconsistency is mainly because over the years new lists were added and over the years the rules for new ones were improved requiring more unique lists with distinct words.