Hard agree on ‘that’s what compiler writers think they’re doing.’ I don’t even think the concept of C being the ISA for some abstract machine is a bad concept. However, and I think it gets to the heart of your point, the compiler writers only do this or adopt this attitude when it allows them to hand wave. There isn’t the consistency that should be present in an abstract machine implementation.

Now that I’ve rambled, I may make the most of this Stay-at-Home situation and write something up using the C as abstract machine concept.