Thank you all, I found this discrepancy in the manual too during the night, it is correct if you take a look at the I/O shield's markings.
🙂Also I couldn't get USB Flashback to work on my USB stick I tried, I had to dig up my ancient USB stick I had at least once used like this with my Rampage IV Gene. And it worked. Too bad the board still doesn't post, the PSU flips itself off instantly when I tried to power it...looks like surge protection is kicking in. Time to try RMA.
Main: i9-10980XE - Rampage VI Extreme Encore - 64 GB G.Skill Trident Z Royal 3600 CL16 - Strix RTX 3090 - Phanteks Enthoo Primo - Corsair AX1500i - Samsung 960 PRO 1 TB + Intel 600P 1TB - Water cooling
HTPC: i7-6950X - X99-M WS - 32 GB G.Skill RipjawsV DDR4-2400 - GTX1050TI - Bitfenix Pandora - Corsair AX860 - Intel 750 400 GB + Samsung 1 TB 850 EVO
All around: i9-7980XE - Rampage VI Extreme - 64 GB G.Skill 4000 CL18-19-19-39 - Strix RTX3090 - Phanteks P500A - Samsung 960 EVO 512 GB - Water cooling