Then I suppose you wouldn't believe that a simple 1/2" hole through the side of a 1" piece of material screwed on the end of a barrel actually makes a pretty effective brake. Believe me, it does. I design and install about 175 brakes/year, on average. I've tested just about every design I can find. I have documented my results, and they would surprise many, not just you. Brake mfgs have done a marvelous job of convincing the masses that their "cool" brake works better than others, when physics, not cosmetics, are where the proof lies. True, some are slightly better than others, just not what we are sold to believe. There's plenty of reading on the subject done by the military if you care to read up on it. It concludes that there are designs that work better than others, but those design characteristics are seldom what we "think" they are. Yes, sail area is important, relatively, but exit hole is moreso. And yes, angle of the baffle makes a difference, but exit hole moreso. The location of the first baffle is also important. That's as far as I'll go into detail. As I said, I also design brakes.lol.
The larger caliber brakes simply have two factors that brake design has not overcome thus far. That being heavier projectiles and a greater area required for the bullet path. Gasses will follow the path of least resistance, normally being a straight line. The greater bore area of the break means more gasses will go unused to pull the gun forward. Small caliber, high pressure cartridges benefit most from brakes. This is somewhat in agreement with what you said about overbore cartridges responding well to a brake.