It’s pretty clear that the design of the Z80 Membership Card is intentionally steered towards the micro-computer ethos. The distinction between a microcomputer and a microcontroller is a subtle one; in fact, it’s up to the use-case whether either term is applicable. Microcontrollers do, indeed, provide lots of I/O and rudimentary computation capabilities - whereas Microcomputers have computing power, of a sort, and some facility for I/O which may - or may not be - expansive.

So the stretch is not much more than a matter of semantics, imho. I’ve used Z80’s as microcontrollers, I’ve also used them as microcomputers.