There are extended ambi selectors just like there are extended SEF selectors.
Also - I like the ambi selectors and packs much better. They don't rely on frictional pressure against the outside of the housing from the selector lever itself. Instead, there is a detent on the internal part of the selector, and a spring-loaded lever pushes against it. They are pretty easy to push from safe to semi, and then from semi to burst or full, but a little harder to reach to push back down to safe.
It doesn't leave that shiny bare-steel arc on the side of the housing either.