I like the strap solution, it's something I would take in concern.
As for the picture, I exagerated the motion of my thumb a little for the purpose, but it can get in the way of the muzzle THAT EASILY in stressful situation...
I have relatively long hand and fingers (I'm 6'3") and it was getting in the front of the barrel easily.
I got my thumb blackened on the side from deflagration one time and since that day, I was trying to figure out a way to prevent my thumb from getting too far on the handguard.
As this shotgun (with this lenght) is considered a self-defense shotgun for large animals (Grizzly, bears, etc) or hmmm Home Hmmm Defense, it's easy in these stressful situations to get your hands in front of the muzzle if you're not careful enough.
Most of the time in these events (when the grizzly charge you or when you go past the corner of your wall, in the dark night) you fire from the hip!
So being able to know where your thumb is resting, is something that comforts me...