This is a good point. I used to ride western equitation/pleasure, and never needed to have my lower leg “on” like for dressage. I do struggle a bit with that on my 15.2 appendix mare as a 5’9" long legged rider, even though she has a pretty big barrel. I usually wear spurs with a longer neck so I can apply aids without moving my leg as much. I ride in a minimalistic monoflap dressage saddle, so that doesn’t add much of any bulk. It is also easier in my jumping saddle with a shorter stirrup length.
5’7, 185 ish pounds, on a 14.3 hand hony that can pretty easily pop over a 3 foot jump with me (though I don’t jump much lately, letting her jump in a couple lessons a week with kiddos and have been playing more with dressage). When I was eight years younger and 50 pounds lighter, I would OBSESS about how I looked on her. Now I don’t care, I go by how she feels and how willing she is for me. (Trying to lose the weight but damn it’s hard, I’m just always hungry).