No you’re understanding is incorrect. There is a big difference between an expired cheque and a reissued cheque.
If I walk into a bank with an expired cheque, they will not honour it, so there is no risk of 2 people cashing the separate cheques. If I walk in with a valid certified cheque, they MUST honour it, even if someone already cashed the reissued cheque.
You are correct that the recipient could wait ~1.5 years for the cheque to expire and then issue a new cheque, but that’s a significant delay and the estate likely wants to close its books before then.
I don’t know. Patrick Stewart seems to have done ok too.