It is an SPC pump. You can see in the picture 12V 6W so its just powered by the 4pin fan cable.
That doesn't make it flawed though. Any more than other PWM or fan powered pumps are. You still just need to give it external power.
Distro plates are very hard to bleed. They take away nearly all the benefit of having a reservoir at all. Its bad enough with a full power pump so with an SPC it can't be much fun. Especially with it tipped on the side so the pump is an air trap.
I don't know much about SPC pumps but maybe if its airlocked it lets the pump overspeed and it trips some sort of built in protection. That's the only think I can think of that would cause behaviour like the OP was describing.