I dont think you ride "faster" standing further rear
But the more experience you get, the more you will like the ability to turn really sharp (or wide) and in control - which is what you obtain with a wide stance and rear foot more aft.
You can control your "height" much faster and be able to traverse waves, or big wind chop, very easy.
Riding toeside, you can avoid getting pulled downwind accelerating to a crash, much better with your rear foot aft, as you can keep the hydrofoil pointing upwind when toeside, IF a rear stance.
Most of all though, you can turn on a dime both from heelside and toeside, as here an even more aft stance is awesome, at least with your rear foot