The high velocity projectile theory, seem sto be proven in a fe instances. But they must be light weight projectiles with thin jackets, with enough velocity to cause teh jacket to fail. Military and FBI tests indicate that for 5.56 projectiles the jacket failure velocity had to be in excess of 2450 FPS to get reliable fragmentation. From 2100-2300 FPS fragmentation could not be relied upon.
In shotgun rounds, bird shot generally makes a wide but shallow wound that will not reliably get to a depth to reach vitals and deep blood vessles, when shot into bare gelatin. Add clothing or light cover and penetration becomes less reliable. #4 BUCK SHOT (not to be confused with #4 bird shot) is where minimum penetration depths begin to be seen.
Now, would birdshot be enought to take the fight out of someone? Maybe. Will it penetrate less dry wall? Yep.
If a projectile has enough penetration ability to reliably get to the vitals of a clothed adult whiel hitting bone and possible light cover, it will also penetrate dry wall with enough energy to do harm to someone on the other side of the wall. Just facts.
I'm not going to argue with those who elect to use birdshot. Your choice.
I'll share a few links to some sites that helped me in deciding what I like to load in my own rifle, shotgun and handgun. Y'all can read it, look at the pictures, and come to your own conclusions. many will argue that FBI minimum penetration standards are not required. That's one opinion. Many will argue that the FBI minimum is indeed the minimum only, that's another take.
Here are some links you may find useful, or may find useless:
This one is more on 5.56 and rifel ammo testing, but you can get an idea of where fragmentation works and doesn't work in certain scenarios. Also Dr. Gary K Roberts research in ballistics is pretty extensive, and if you google his name and ballistics you can find lots of useful articles.
Again, not trying to start a fight or contradict someones choice, but sharing some facts adn tests that may help the OP in choosing what he wants to use in his Maverick, and shed some light on where the high velocity fragmentation theory comes from and what some of the limits are, from research that has been conducted.