This happens with desert villages overall, even in normal worlds. These bushes seem to be hardcoded - they keep generating in villages, even if you disable them with datapacks.
I tested creating superflat world and go around to find some desert villages and I didn't encountered the problem of the report. However I found a dead bush generated a lower block in a desert village but in a normal world, not superflat. Maybe I should modify the report?
Here the problem: minecraft:village/desert/streets/straight_01 has an unnecessary dead bush on a lower level of the street, this causes the block to generate in this way.
Can confirm in 21w16a.
This happens with desert villages overall, even in normal worlds. These bushes seem to be hardcoded - they keep generating in villages, even if you disable them with datapacks.