Yup all those points and some guys have a preference to push the red dot further away and open up their eye relief. Some times its dependent on the type of AR as to where they can mount it. As with that image they have fixed carry handles and no mounting point or rail over the receiver and have to use the hand guard rail. Sometimes it can be that the optimal point is over the gap or join between the receiver and hand guard rails which isn't really feasible. The Israeli's had an adapter they commonly used for their issue reflex sights on AR's that had it just forward of the carry handle. As below some prefer it a bit more forwards depending on what works best for them.
