i used to straighten out the leg too until i was told that i created tension around the area between my hips joints, the creases in front of my crotch. also, the opposite muscles behind my buttock also tensed up. essentially i created corners and creases at various area around my groins and hips. easy to create braces. so i was told to keep things round and soft and no creases, sort of like arc/bow shape.
I'm not sure if I'm doing it right, but my leg becomes straight when I do it. I think it helps with the suit stretch in the legs and helps connect it to the body. It's not locked straight of course. So maybe it does stay soft and round, like your hips, Phi.