Sorry I don't see the relevance of CPU having any hidden global state in the thought experiment I've addressed. If all I give you is a PGP file made on the Intel CPU you simply don't have access to the global state of my CPU and I can be sure that I'd get exactly the same file up to the last bit using non-Intel CPU starting from the same inputs (including same 'seeds'). So I can actually be absolutely sure in AES instructions for any scenario where I only give you the results of encryption.