I'm glad your problem is solved, but PWM (Pulse Width Modulation) is the proper setting for a PWM fan motor. Either the PWM function of the DC fan motor isn't working, or the board/BIOS has issues. You are plugged into the correct fan header, right? You don't inadvertently have the CPU fan's and a case fan's connectors swapped, maybe?
I understand, ive never had this problem before i had a 3000G and ryzen3 3200G with A320MH setup, and i dont recall having these problems, but then again i sold these PC's on quickly so ill never know unless i get a complaint. then again the 3000and 3200g dont have wraith spire cooler.
I'm still leaning towards throttling as the cause, its a fresh built PC, the mobo arrived with the F50 latest BIOS and everything, there is a setting in the BIOS for "custom throttling" so im assuming i could mess around with that and probably fix it (never dealt with throttling in BIOS before so i noobish), but in all honesty VOLTZ setting is perfect and working great, i dont think im going to fug with it for now.
The FAN never goes to its 3000rpm max under load on VOLTZ, like it did with PWM., and the temps are all sound and equals or better, never gets abouve 65. PWM setting is automatically overkilling it on these Ryzens, someone call AMD lol tell them pwm settings are fug'd. lolol