8.11.9.866, but walls and slabs don't get their DG-info removed.
It works on Smartsolids or Form geometry you created and then added DG data to.
It won't work on things that were created DG-aware.
A Wall will remain a wall, a slab will remain a slab. TFREMOVE strips all intelligence (incl. quantities) from a wall. If you add DG slab properties to that "broken" wall, it won't have the right slab quantities. The are Linear Forms and Slab Forms, no way to turn one into the other that I'm aware of.
I could imagine Slab and Wall being similar enough so that a block that was placed as a wall instead of a slab should be interchangeable, but a bathtub and a wall might be a bit more challenging to say the least. Adding Slab DG info to a Linear Form can be done, but again it won't find the quantities.