While shoring up nomenclature: I believe “simultaneous multi-threading” (SMT) is the generic term and “Hyperthreading” is Intel’s branding of their SMT implementation.
Calling AMD’s SMT “hyperthreading” is like calling all tissues Kleenex. It’s fine imo, but it doesn’t hurt to know these things.
No, they were almost certainly talking about some part of their build process limited it to a few processes (like maybe a 'make -k 6' limitation), or something that could be easily parallelized.
It was worse than even that, several parts of the build process were fully sequential. I only got benefit of multiple cores at all because the tooling in those sequential steps were utilizing it, or related system services were.
But, yes, I also did change at least one config to allow it to spawn more than 2 threads.
Not sure how that would be in any way relevant to the parents point though.