Most likely it tries to print rich black, which uses color to make the b&w printout look better ( and use up all that costly color). You can disable that in your printer settings with most printers.

I heard that before, I think it's a tactic to bully people into buying more ink they don't need. Ensuring tracking dots is maybe just an unfortunate side effect.

I've always assumed that is just lazy design (some resources that _might_ be needed are unavailable, report and refuse to print withut checking if they are actually needed for the current job) rather than due to a security (or even ink selling) measure. I've seen the behaviour as far back as the first colour photocopier I ever used.

I've seen that as well a long time ago on a black+red photocopier, no yellow and probably no tracking patterns since red would have been quite visible.

No, the thing happening does not count as proof why it is happening. Printers refusing to print bw is widely known.