Yea so first of all, I googled her. I would say her legs are pretty good sized, lol. They aren’t small. So there’s that.
Then, as eyedentist mentioned, you’re confusing direction of correlation. My point was that if you have big, muscular legs, they will be able to lift significant weights. Nothing you said contradicts this. You provided an example of a 1rm from someone, when I was talking about 10rm. She clearly has a very efficient nervous system, as do all elite weightlifters. I said big legs will be able to move big weights. Which is true. I did not say there are not examples of folks with smaller legs who can also move big weights.
Heavy weight, low rep training is something that i am trying to implement as well. I start every body part with a compound movement and work up to a 3-4 rep max. After that my reps are in the 8-10 range. For quads i might go as high as 15-20. I have been enjoying it so far.
Apart from all the reasons already mentioned, there’s injury prevention. Higher rep work doesn’t just make muscles grow, it can also help connective tissue get stronger. Training heavy all the time is hell on the joints.