The stronger you are, the easier it is to overpower someone using muscle without realizing that that's what you're doing.
A couple of years ago, working with a partner about 50# smaller than me, I felt like I was doing great, moving smoothly and easily, getting through the technique. Sensei clapped, we sat down, and then after the demo moved on to different partners to work some more on the same technique. This time my partner had about a foot in height and maybe the same 50# over me. I tried to do the same thing I had before, and surprise! It didn't work at all. I had been blitzing my first partner without knowing.
Larger-than-average people have a disadvantage here in that they rarely get to work with people bigger and stronger than them; they don't get to run into the brick wall of muscle that they're presenting to smaller people without even realizing it. If a big person is only using 15% of their strength, they can still totally overpower a small person, using that muscle alone, even if their technique isn't perfect. To the small person it feels like they're being treated like an inanimate object.
A good example is stick work - a big guy can come in off the street and make really satisfying whooshing sounds with their shomens right off the bat, even if their technique is horrible; a smaller person has to learn how use their power more efficiently before they can play with noise that way.