Judging by the weapons you have listed as what you use and base this opinoin on, I can see how and why you would say that.

The recoil out of a premium semi-auto is more manageble than you would expect. If you have only shot 3-1/2" fodder out of these weapons and not a top end semi-auto, you would be quite surprised out of them. I have shot over 20 cases of 3-1/2" in 28 states, Canada, Argentia and Mexico at waterfowl. I feel that I would have to slightly disagree with your observation as I am sure others here will as well.
Try taking a crippled goose at over 70 yds with just a 3" round for a client that chipped him with 3 rounds and now you have to try to cleanly harvest that goose before it reaches the refuge where you CAN'T retrieve it!! Thats where 3-1/2" REALLY shines, in both 12ga and 10ga.
I agree with you that 3" is very manageable especially in top end semi-autos. And like CrimeDog said, all of my waterfowl weapons have overbored barrels and aftermarket, extended, ported chokes. If one of your friends has one, try it sometime while waterfowl hunting and not at the trap range where you will be focusing on the recoil and not the actual weapons performance. My .02 cents.