Physics decided everything for Us long ago! The speed of the harpoon is 33m per second! Speed of sound = Velocity of air movement = 330 meters per second! A hole even half the section of the barrel does not affect the piston speed if there is no excess oil in the barrel of the rifle! Learn Physics Friends! All valve guns are based on this!
Please quote exactly where you got this from or elaborate somehow.
I have been looking for an answer to this exact question for a very long time and your answer does not align with the anecdotal evidence from the many people who pull out the power regulator and swear they see quite a bit of improvement.
I have long wanted to find a fluid dynamicist and pick his/her brain on this matter as to them, it's probably a fairly easy question to answer but I have yet to bump into one.
Now, if the question is whether you would want a gun with or without PR (Power Regulator) I would say it depends on your hunting grounds and technique. If you are shooting a big gun in blue water, then no need for a PR and I would personally pull it out. But the last few weeks I have shot a friend's Predathor 100 on the reef and even with the PR bulkhead doing a bit of throttling it's still powerful enough for the fish I can run into here. But having the PR is such a nice feature and the kind that you may not think you need before you have it.
E.g. two days ago, I shot seven fish on the reef, four of them was on full power as they didn't come super close but one of them came right up to me and even though there was water behind the fish, I shot it on low power to have the easy reloading when I surfaced. I also shot two red Googleeye fish in some deep caves. These fish are fairly small but very tasty so I sometimes take them if nothing bigger is around. But they like to stand right next to the wall but with the low power feature I had no problem shooting them up close and still not risk bending the shaft or getting it stuck. With a rubber gun, unless I had air left to unhook one rubber, I wouldn't have shot those two fish.
So, in short, for a reef gun, I would say go with the power regulator
