They slowly moved the business logic out of TPF ASM to x86 app servers, which left the TPF machines as mostly distributed NoSQL servers. Then they replaced that layer with Couchbase or similar. Took 15 years or so.

TPF itself, and the programs written in it are mainly in s/360 asm, so I doubt very much it's running on x86 now. It's so s/360 it doesn't have traditional stacks.

Is there a way to reconcile these two above responses? They seem to be very different answers. Are these both options that a customer can choose from?

Yeah, it sounds like they rewrote it piece by piece to run on different architectures.

Really similar to having a big monolith, and taking pieces out chunk by chunk rewritten to run as microservices until you're left with a new codebase with no sign of the original monolith or any of it's code.