In general I agree with you, but I see the point of requiring proof for statements made by them, instead of accepting them at face value. In those cases, given previous experiences and considering that they benefit from making them, if they are believed, the burden of proof should be on those making these statements, not on those questioning them, no?

Those models seem to be special and not part of their normal product line, as is pointed out in the comments here. I would assume that in that case they indeed had the purpose of passing these tests in mind when creating them. Or was it created for something different, and completely by chance they discovered they could be used for the challenge, unintentionally?

Yeah, that's how the concept of "reputation" works.

No, they are likely lying, because they have huge incentives to lie