Sure, but if something is agreed upon to be a bad idea and the few implementations that exist implement the bad idea, removing it from both could help prevent a bad idea from spreading.
I’m sure nostr:npub1xdtducdnjerex88gkg2qk2atsdlqsyxqaag4h05jmcpyspqt30wscmntxy added the L tag without looking at it too much: “it’s in the spec, the only implementation uses it, I’ll copy it”