This is what bothers me about the characterizations of CPU architecture in ELF files and (IIRC) Python eggs... They're so vague about which particular x86 ISA

This is what bothers me about the characterizations of CPU architecture in ELF files and (IIRC) Python eggs... They're so vague about which particular x86 ISA variants are compatible with the binaries. So, e.g., a program loader doesn't necessarily verify that the binary will work on the CPU. Or, as we see with Linux distros, they build packages for the lowest common denominator ISA. (Note: it's been a while since I dealt with this, so I might be remembering a bit wrong.)