Hi KnarfeX, if I remember correctly, the tachometer lead can be connected to any fan header in theory. Whichever one you choose will read the pump speed. I can't think why your OPT-fan and CPU-fan indicators seem to be the wrong way around. Were you connecting to the correct pin? Anyway, it is working and that's the important thing. Have you installed the iCue software? My lead is connected to the CPU fan header and it works fine. Have a look using HWInfo and see what that says as well.....
Note that I have a different motherboard but the same cooler. It would be very surprising if the fan headers were labelled incorrectly though.
Z690 Hero, 12900K, BIOS 3701, MEI 2407.6.1.0, ME Firmware 16.1.32.2473, 7000X Case, RM1000x PSU, ASUS TUF OC 3090TI, 2 x 16GB Corsair RAM @ 5200MHz, Windows 11 Pro 23H2, Corsair H150i Elite AIO, 4x Corsair RGB fans, 3x M.2 NVME drives, 2x SATA SSDs, 2x SATA HDs.