I think this is very cool, even though I have no historical connection to the Z80 it's of course a well-regarded and firmly entrenched/popular retro CPU.

But this really is a stretch:

The Z80 Membership Card itself is a stand-alone single-board computer that can "power up" your projects, like the Parallax BASIC Stamps or Arduino microcomputers.

Both of those are very commonly called microcontrollers, not microcomputers, since they have all of those extra chips merged into the single package of the CPU.

Take a look at the Arduino Uno [1] which is a very typical (if old) example: you will see that the board is not covered in ICs from edge to edge, since all of the main functionality is in the single-chip microcontroller. I think the second big-ish package visible is for the USB, but that also disappears on more modern controllers with on-board support for USB.

[1]: https://en.wikipedia.org/wiki/Arduino_Uno#/media/File:Arduin...