Ha! I should have researched that instead of relying on my fading memory of the era. I'll footnote your point when I get a chance to update the post.

Also, PS2 mouses and keyboards have physically identical but electrically incompatible connectors, which is like a precursor of the nightmare that is USB. ADB is positively magic in comparison.

And not hot-pluggable. I lost track of how many motherboards I had to replace due to hot-plugging PS2 devices.

Note: keyboards and mice were pretty low risk. High risk were PS2-based barcode scanners.

Well, nothing will break if you mix them up. It's just the command protocol which is different. I recall there was a Linux hack-patch which could use an extra keyboard in the mouse connector.

Not to say there weren't problems. I had a Compaq couldn't speak to most PS/2 keyboards, so when my keyboard broke, I had to go find another Compaq keyboard on campus before I could use the computer again.

Sudden flashbacks to the "PS/2 to USB" adapters that came with some keyboards, but were just electrical connections, no adapter at all. So they'd only work with keyboards that were able to speak both USB and PS/2.

The (1984) PC/AT keyboard has the same protocol as the PS/2 keyboard.

and a connector that is 5x the size of the ADB connector. I mean, just look at that thing. It's huge. It's ginormous. No wonder Apple didn't go with that thing. Instead, they used a connector that had pins that would easily bend if it was accidentally attempted to be inserted into the wrong port.

Worse, that connector was used on all sorts of things. That same connector was used for power delivery on some computers, midi keyboards, and monitor outputs. People blew up their sewing machine plugging a keyboard into a port. I'm sure there were more uses of that same connector for other things that were electrical incompatible. At least the PS/2 (and ADB) ports were used only for one purpose (PS/2 two - they should have either made mouse and keyboard interchangeable, or made them different, but just keyboard or mouse was a big improvement).

They could have picked the PC keyboard protocol and used their own connectors, if they wanted to.

Almost every time there is "Why Apple did X while Y was available" shows that X was released before Y.

While Apple couldnt have used PS/2 mini-DIN connector, they could have adopted electrical signaling and protocol as it was reused from 1984 AT keyboards.