One can I presume call it whatever they desire. There are two ways it can reduce recoil. First is by reducing overall work done by the expanding gases, resulting in a reduced velocity of the shot load. This affect would be less than a reduction of the bbl length to the point where the ports start as not all the gas is diverted. 2nd is closely related ie the gases themselves are diverted from exiting the muzzle, thus not adding to the recoil. "IF" the ports do this then they serve as a "Muzzle Brake", "IF" they don't act as a muzzle brake, they don't reduce recoil, elementary. If you look at the scenario I gave on the load, which was weighted a little on the powder charge, most target loads will use less than 26 grs powder, "IF" the entire powder charge were diverted & not allowed to escape the muzzle forward the max reduction possible would be less than 5%. These little ol holes aren't going to anywhere near that effecient.
"Surgical Precision", I can assure you I'm no surgeon, but I have operated an EDM machine. "Some" of what they say is "Partial" truth.
