I think your theory is right.

Beside, zm is mining devfee on zcash flypool (see here: https://zcash.flypool.org/miners/t1NEpmfunewy9z5TogCvAhCuS3J8VWXoJNv insane, am i rite? )
and WaveRiderx is probably mining another coin on another pool with obviously different difficulty,
so counting * an + is a waste of time.

I've checked the devfee, it is exactly 2%.