Hello Janluc,
Correct. The reason you are able to get video on your D6000 dock or our UD-6950H dock over USB-A is because these docks use a technology called DisplayLink, which essentially converts the video data to USB data, transfers it through the USB port, then gets converted back into video data by the docking station. Our TBT3-UDZ does not use this technology, so it will not work on a USB-A port. However, this dock should still work well with the M1 Pro MacBook Pro as it has Thunderbolt 4 ports.
Thank you,
Evan
Plugable Technologies
www.plugable.com/support