> I would like to point out that a phone doesn't need active cooling.

A single phone, far away from other sources of heat, used only in environments that are comfortable for humans (which may well involve active cooling at the building level), and configured to throttle down when it's used for more than a few minutes, perhaps not (although even then, I've seen phones get uncomfortably hot when gaming, and had my own phone shut down because it's too hot on occasion). If you were setting up banks of phones to run in a datacenter environment, and expecting to run them flat out, you'd probably want to actively cool them.

> And I don't know if that statement is accurate, since passive cooling would be even better than active cooling from an efficiency perspective and particularly if you also consider reliability. Less moving parts would mean higher reliability unless, eg., the thermal paste evaporated on the cpu.

Everything is tradeoffs. Per recent posts here, the likes of AWS are now at the point of cooling CPUs directly with datacenter-scale watercooling; essentially the building's air conditioners, rather than terminating at a fan unit on the inside, feed cooling water directly to a plate mounted onto the CPU heatsink.