he never would have gone into a combat operations area with a .22 as his sidearm.
I agree that is a completely reasonable assumption. Patton had been in personal combat in Mexico, and in France before WWII, so I think he would have made a logical choice for a combat sidearm.
Also he was an Olympic class shooter, who was probably robbed of a medal by a judge's decision that he missed a shot, rather than accept what likely happened, two bullets went through the same hole.
SO, yes, I'd think he knew what it was all about.
On the other hand, if I'm in an assembly area, 40 miles behind the front, or if I'm in Texas, and there are rabbits, or other small game about, I might just pack a .22 for that trip. And, might even be wearing it when some photographer wanders by....
Rommel, and some aides, on at least one occasion hunted gazelle with an 8mm rifle while in Afrika. I could find no details on the specific rifle or ammo used, other than the mention of its caliber.
During the opening of the Battle of the Bulge, some senior Army commanders (not looking it up right now) weren't at their HQs, a couple were in Liege, getting "fitted" for shotgun stocks at FN....
Generals, pretty much, do as they please in lots of things....