Because there is no sulcus anymore. It's a unicameral eye at this point. The point of a SFIOL is that there is in adequate capsular support, hence the suture supported IOL. And the lens is some ways from the iris to prevent chafing (which can happen)
It does if it’s not placed posteriorly enough and then there’s probably more risk of tilting. The haptics could be amputated to reduce the risk, since the are not needed for anything. Luxated and scleral fixated in-the-bag one piece IOL’s are less prone to causing UGH than these without capsular bag. A toric lens designed for scleral fixation (or even a toric 3-piece IOL) would be ideal, but none are available in the US afaik, so people have to come up with different ways of going around the problem.