The caption should read recommended "maximum" rpm, because it has not much at all to do with cutting procedure, but liability lawyerspeak. At 2000 rpm the same spot comes by the tool 33 times per second. The first time it comes by, the wood's removed, the rest of the time you're cutting nothing. Now figure you can advance the tool ~1/8" per second under control, if you're normal. Wants an rpm of ~600 to hit every spot twice.
On the flip side, you've got Newton who says that you have twice the velocity, you have 4 times the energy for your face to absorb if you hook and throw.
I believe the rpm given represent a suggestion for people using scraping technique, not cutting, and pushing the tool straight into the rotation. Both possible, but poor choices. The man who coined the term "spindle roughing gouge" is one of the push in at 90 degrees, based on his old JET youtubes. Wonder he didn't hurt himself, though, if you look at the surface, he left a lot of roughness to work out. Guess that was his penance.
All you need's the gouge. P320 would roughen the surface.
Better to follow the leader than the pack. Less to step in.