On top of that, some customers mandate a specific ISA or even a specific vendor, so none of it is truly fungible outside vertically integrated workloads like S3.

I would be very interested to be a fly on the wall when a customer attempts to mandate to AWS they must support an ISA that AWS doesn't have plans to support out, say, a decade[1]. That would be almost as amusing as the many, many times I've heard clients say "we spend $X million dollars with Microsoft! We're a Big Company! We have leverage! Of course they'll do what we want!". And the local M$ salesthing just smiles nods and says "I'll get back to you on that..." and for some reason Nadella doesn't return their calls.

[1] Maybe if one of the big nations says "thou shalt only use our glorious domestic processor, and the processor of thine enemy shall be verboten, for all the data things" or some such...but not a commercial enterprise.