I don't care at all about this discussion! I was just trying to ding the commenter for going off on a tangent. Also, the person I'm replying to wasn't talking about instruction-level parallelism, they were misreading the article.
> In a world before multi-core processors, these threads weren’t actually running simultaneously
He's trying to describe the difference between multi-threading and multiprocessing to introduce the idea of task switching. But the bad history lesson is distracting.
There were long periods of history when most hardware vendors had at least one model with multiple processors, and there were some companies that specialized in them (Cray, Silicon Graphics, IBM, Fujitsu, Toshiba?), including ones built with x86 processors (Sequent, IBM).
It doesn't say computers could only execute one instruction at a time. It says processors.
If you're going to do needlessly pedantic bikeshedding, at least get it right.