Waterlogged blocks are not accounted for when calculating water depth for map rendering purposes

See attached screenshots. Between the 2 redstone blocks at the bottom of the map, the top slabs should (like the full blocks next to them) make it so water depth at that position is calculated as 1 block deep. After all, waterlogged top slabs appear as slabs - and not water - on maps.

Probably also affects stairs, and potentially other waterloggable blocks with full faces.