Not on strict reading. Stating a true affirmative doesn’t mean the negative is false. It’s like saying “In Denver visitors will have blue skies.”. It doesn’t mean that if you leave Denver, you leave blue skies. For that to be true, the statement should be “Only in Denver is the sky blue” or “You MUST be in Denver to see blue skies.” There’s no Only or Must in the wording from Disney.
Similarly, the fact that off-site guests only have 30 days doesn’t explicitly exclude anyone else from making FP arrangements then. That’s like saying “Visitors to Seattle can expect rain.” Well, it rains in Denver, too. One statement is not related to the other. We put them together in our minds, but they are completely separate statements.
Furthermore, the gold standard is what’s in the Terms & Conditions of one’s room agreement. Fastpasses aren’t even listed!! I encourage everyone to read the fine print. Disney basically can change anything at anytime for any reason. They are deliberately opaque about this and many other issues for a reason- it’s less trouble for them if they change their policies.
And finally, there is NO language anywhere, as I am making or reviewing my on-site reservation that mentions 30 day FP for onsite guests. No. Where. I wouldn’t even know that’s the new “policy” that people say I’m subject to if I cancel my leading reservation. But I’m not subject to it. We visitors are literally making up a rule that Disney doesn’t have, by linking two statements that are neither linked semantically or in practice.