This is in-line with my experience on the road. When I went from 16mm To 21mm ID rims on my road/gravel bike, I was able to run the identical tire lower in the front without feeling it squirm under hard cornering on pavement.

Many people report the same thing with mtb tires, though I have never had the chance to test the same tire on 2 significantly different width rims. This may not be an issue if one runs higher pressures, but as people chase the lowest pressures they can get away with, tires squirming in corners or off camber scenarios is one of the limitinng factors. I know for me it is on the front end of my FS bike. And rim width (along with sidewall construction) effects this.

Rim width also effects the tread profile. With a narrow rim, you get a rounder profile and need to lean the bike over more to get the side knobs to connect. With a wider rim, you have a more square profile, and the knobs hook up with less lean. Too wide, and you start having intermediate or side knobs hooking up too soon (or all the time) and it just slows you down.

Peronally, if I were building a new set of wheels for what the OP is describing, I would go with something like 23mm ID. Maybe even a little wider..