the speed readout missing is why startup boost goes up and down, it is required for the controller to know it managed to kickstart the fan.
that said it's not really required to use it if your fan curve doesn't start really low like 200 rpm or so.
If it is just one fan misbehaving, what happens if you connect all the fans to the Quadro, but make another working fan be the one reporting speed?
I have 10 ARCTIC P12 PWM PST fans. None of them show speed when connected to a Quadro controller.
When connecting any of the 10 fans to the fan header on the motherboard, rpm are displayed normally. The problem is in the ARCTIC P12 PWM PST + Quadro combination. Separately everything works well. I think that the reason is some tricky rpm signal from these fans, which was not taken into account in Aqua computer.