It will auto remove when foundations/Pillars are placed, but, on rerender, is back.
PC
No Mods
Dedicated server app
By Crom’s thundering backside, this cannot be!
You can not Stop Grass!!!
I’ve actually had it re-appear several times now on 3.0.5. It seems to be conditional i.e. something happens and then it appears for that session, but when I log back in it has gone again.