Not an option for us pot bellied old men.
I believed this, too, but:
I just finished a two-day handgun course for CCW carriers focusing on improving speed of draw, accuracy, etc. I was shooting my P365X, a micro 9, from an OWB holster. On the second day, the instructors encouraged me to try a larger gun, an H&K VP9.
To my surprise, they set me up with an IWB appendix holster.
I say surprise because I have that pot belly. They set me up with an inexpensive plastic/kydex, IWB holster, and taped what they called a "wedge" to the bottom of it, between the holster and my lower andomen, so that the gun straightened up, rather than pointing towards my body, because the base of the holster was considerably larger than the top.
(They also taught appendix carriers, which comprised at least half of the 20 students, to thrust their bellies forward and arch their backs rearwards, limbo style, when reholstering, to keep the muzzle away from the body.)
Not sure what the "wedge" material was... Something with a consistency between styrofoam and foam, it felt like. Anyway, it worked quite well.
I had never come across the "wedge" concept before, but found it surprisingly effective for comfort and safety.