And apparently the plan is to have explicit sync ready for the next major driver version (v555).
From the discussions on Github and Gitlab it seems the work for that to happen is done. The changes in the necessary packages (Xwayland, Mesa?) just need to be merged and the the Nvidia driver 555 needs to be released. It hasn't been that long since the previous release 550. So I guess it is going to take a bit of waiting still.