Unbelievable. An experienced & successful entrepreneur would take on an unknown cofounder without any kind of vesting schedule + cliff. Doesn't make any sense to me. I am not buying Jeremy's side at all.
He submitted a YC application that listed them as co-founders, and has no paperwork showing the Jeremy gave up his share (whatever it might have been).
So, the only explanation I can come up with is that " An experienced & successful entrepreneur" took on "an unknown cofounder" without proper paperwork.
That's a pretty surprising set of circumstances, but it seems pretty clear that it happened.