Billyball,
Yeah, this actually can be a thing. I tend to think along the lines of Buckeye in that it makes no sense to dress in baseball pants as a coach. Our fed also requires it for games so, of course, I complied there. At practice, i'm in sweats but always in proper team attire and hat as were my assistants. What was important to me was that we wore something practical to actively coach in while clearly wearing team gear and having consistency with our guidelines as a staff.
I had an old school assistant for the last several years who was a previous HC and AD at other schools. He came in baseball pants (and polished shoes) every day. I get what was behind the thought process. It was never brought up as an issue with the players. There was never a doubt that we both were all in and were on the same page minus that one exception.
I've seen it both ways in our area. More don't wear bb pants than do. I don't see any pattern of separation with the more successful teams.