They're computers based on microprocessors. Hence, microcomputer. We often called them "micros" for short. Many Brits still do.
I know that "PC" now means "capable of running Windows", but back in the 80s and early 90s it usually meant more literally "personal computer", which was a synonym for "a computer small enough to fit on your desk".
The only not-really-an-exception exception in the article would be the 32-bit Acorn Archimedes; it was generations ahead of the other (8-bit) machines listed, and "microcomputer" is really associated more with the 8-bit machines in my mind, but I think that's because by the time I encountered 16/32-bit machines (Commodore Amiga, Atari ST, 386-based PCs, the Archimedes) in the early 90s, the term "microcomputer" was falling rapidly out of fashion. Those more powerful (and expensive) machines actually launched in the mid-80s and were absolutely still microcomputers in the parlance of the day.
The Apricot PC ('83), Apricot PC Xi ('84), and Apricot XEN ('85).
I actually used the XEN at the time, since a relative had one.
However these were not IBM compatible, in that they used different support chips, and had different memory maps.
The Apricot XEN-i ('86) actually was IBM PC compatible.
PC is only synonymous with Wintel because everything else died except the Mac, so the terms were essentially interchangeable.
Mainframes = room sized montrosities
Minicomputers = multi-cupboard units
Superminicomputers = just one cupboard or small fridge
Microcomputers or personal computers = these guys in the article
This was around when the most portable computer was not known as a “laptop” but a “luggable” due to its mini-fridge-like nature.
Since it is so personal, the iPhone should probably be named PC above any other device.