does this statement apply to projectiles rotating due to the grooves in the barrell
Ummm, yes. Why wouldn't it?
Stopping power is a myth. The idea that you can say "Okay, this round will stop someone 80% of the time if you shoot them in the torso" is deeply flawed; there's a lot of variables to consider with gunshot wounds.
The bullet velocity, construction, calibre, shot placement, angle, depth of tissue it passes through, the person's clothing all influence the severity of the wound.
Bullets create two things when they pass through tissue; a temporary cavity and a permanent cavity. The temporary cavity is a temporary inflation of the surrounding tissues caused by the bullet's passage, as most tissue is elastic. The temporary cavity by itself causes very little to no damage to most elastic tissues, like blood vessels, however, it can cause a rupture of fluid filled organs like the liver or brain.
The permanent cavity is the actual physical hole caused by the bullet
Read these articles for more information;
http://home.snafu.de/l.moeller/milit..._patterns.html
http://www.firearmstactical.com/hwfe.htm
http://teapot.usask.ca/cdn-firearms/Fackler/wrong.html