it's because they want to keep it save for some mobos only have one dynamic speed fan, the CPU_fan...
"Only Gelid fans" is marketing bullshit.
PD: I have seven 12cm fans and no hub.
a) 3in1 at top
b) 3in1 front ( radiator)
c) 1 rear
Using only 3 mobo headers.
a) and c) are set up to stay...