pt22064
Your introductory sentence is only partially true. If the organizers want their tournament to be rated by FIDE, USCF, or any other sanctioning organization, the organizers cannot implement rules that conflict with the sanctioning organization's rules.
Yes, that is true. If the tournament rules do not conform to FIDE/USCF rules, then those organizations will not recognize that tournament. I would posit that most people don't care whether the tournament is "official." The prize money probably matters more to the average person.
According to the arbiter guidance document, the claim has to be checked by the arbiter if it occurs before the agreed draw move restriction.