Speaking of finishing subfloors, years ago, perhaps fifteen or so, I recall sanding and finishing a wood subfloor that consisted of 2x4 pressure treated doug fir built up on edge. They had glued it and run long 3/4" bolts through the middle of the 2x4's. These rested on pressure treated doug fir beams/girders. Why pressure treated? The house was next to a river and built about ten ft. of the ground. Sanding those uneven 2x4's was a nigthmare. Had to start with #16 to grind them down to get close to even. After sanding, stained and finished them with poly. The homeowners thought they were great, probably because they saved a bundle by not installing flooring. I thought the floors looked weird. Man, the things I used to do.

I wouldn't even consider it today because of the pressure treatment.