"Proved" means demonstrated with a formal mathematical argument.

"Proven" refers to something confirmed over time, often used more informally.

"Proofed" is an editorial term—preparing text for publication.

To people who accept "proven" as the past participle of "prove", there is no difference. The only reason it would be rejected in English writing about mathematics might be that a good many of mathematicians are also pedants for prescriptive grammar. It is not a mathematical issue whatsoever.