I'm not sure I'm for these. First, it's only six shots. Most standard defensive shotguns carry more ammo.
Second, it's a completely new way to reload, which is different than normal shotgun procedure. While reloading a full magazine would be faster, it doesn't make sense for me.
I've been to one shotgun class, albeit a beginner one, a long time ago. "You fight with what's on the gun" was what I was told, and when I read about guys here doing advanced level shotgun classes, they say the same.
I don't see you grabbing another magazine in any scenario. If you planned to bring extra magazines, you'd probably want a rifle.
Additionally, you can top off with the traditional setup.
While I'm glad the firearms industry is coming out with new things, this isn't for me.
I'm going to stick with magazine extensions and side saddles.
My two cents.