[ilyt]

I'm surprised it doesn't mention hysteresis some fans have at low speed.

Cheap fans often don't have actual proper speed controller on them which means they might start spinning at say 30% PWM but only stop spinning at 15% PWM. That was probably the thing that surprised me most when I upgraded to nice Noctua, at certain PWM it just started, always, and below that it stopped, always.

[paxswill]

Those fans that start at 30% and then allow you to go lower are explicitly allowed by the spec from Intel (linked in the article, sec 3.2 and 3.4).

[ThePowerOfFuet]

Allowance in the spec doesn't mean that behaviour is desirable.