I own three 870s set up for defensive purposes.
None are for house use.
After clearing houses & buildings for several years professionally with ARs, shotguns, and handguns, I found the handgun infinitely easier to work with around corners, blind angles, through doors, up stairways, and anyplace the off hand was temporarily needed (opening doors, closets, moving things out of the way, etc.).
I see no surprise whatever in anybody deciding to go with a handgun vs a shotgun indoors.
Outdoors in more open spaces, that'd be a different matter.