"Even if we assume most of those are the cheapest M0 class running at 100MHz"

https://s-o-c.org/arm-cortex-m0-clock-speed/

Even if it's an order of magnitude less it's still a lot of compute ;)

What the author of the article forgets is those microprocessors will use a lot more power if used 100% of the time, so there's no 'free' compute in that sense.

Also the author of "Massive hidden productivity sitting idle in sleeping humans, usable for increased profits".