Bristolskier, that is correct. I did that on my Impact 10s to make them a little more livable off-piste. The boot is still pretty damn stiff even without those screws in place.
I did pull out the threaded inserts from the inside of the shell after removing the screws. A couple of them were loose anyhow, and I didn't want them to fall into the boot or get out of place and cause damage to the liner. The others were easily pried away from the shell with a flat screwdriver. Keep them in a safe place with the screws in case you ever want to reverse the procedure.
I found some plastic hole plugs at the hardware store that fit the outer shell holes almost perfectly, and glued them in with a bit of caulk. That should take care of moisture entry for the most part.