From the YC application video alone, there seems to be a major point of contention about what Jeremy actually contributed. In the video they are talking about specific plans involving commodity hardware, that they devised a way to constrain the engineering problem to make it feasible, and that they had co-developed a business plan to get it to market quickly.
That's all just plainly in the YC application video.
That doesn't seem compatible with what Sam Altman says, so either the video does not depict Jeremy's contributions up to that point in time, or else Sam is incorrect and has omitted many contributions from Jeremy. Those contributions may or may not justify Jeremy's claim, but they certainly complicate the issue and present a very legitimate position for Jeremy to at least make the claim.
Jeremy's claim may ultimately not be considered or may not be upheld, but either way the degree to which Altman seems to think it should be categorically ignored does not seem to match the facts regarding the initial formation of Cruise at all.