Doesnt seems like metadata.nostr.com is doing that, maybe you should reset your key manager permissions and just manually approve every signing until you're satisfied that its not adding LUD06
Discussion
I think any client that lets you update your metadata without letting you select your preferred relay, fetching it and actually waiting for EOSE and showing you what the change will be is asking for trouble.
i do recall one day i did use nostr.com in recent times and i remember thinking oh cool, they support nip-07 sign in now. i signed in, poked around, but didn't do anything and i haven't been back to that site since that day. i will test. thank you again.