I don't think individual deposit holders technically have a legal contract with the FDIC. Are you sure? Do you have any sources on that?
You are right in practice that the FDIC guarantees small deposits.
You are right in practice that the FDIC guarantees small deposits.
If it was just a legal contract, in the worst case you'd have to sue to hold them to account.
(On the other hand, politics can change from one day to the next; but contracts are harder to unilaterally change.)