Well, literally and figuratively in this case ;)
When I render the attached scene to PV/viewport/VFB, I get the desired result.
When I render to IR, I get a very clean toilet, but not quite what I had in mind.
I need to switch off the SDS to make it work (or dial the subdivision down to 0.
Win 10, R19.053, latest beta 2 (from March 21).