I've actually played with both positions and find centering the boot works best. Too much toe overhang and you lose heelside leverage and spinning off the heels becomes very difficult, and having the balls of your feet over the toe edge give too much power transfer to the edge that already has the advantage in that area. Plus toe drag pretty much limits how aggressively you can lay a carve. This would be the least ideal boot position.
Having more heel overhang puts the balls of your feet closer to the center of your board and actually increases control, especially off of jumps and sliding boxes and rails, and the heel overhang adds more power transfer to the heel edge. The downside is it also increases your chances of hanging up on an edge when you're boardsliding backwards, which I found happened alot. Centering the boot is the best way to go.
Personally, I think the kid was just BS'ing you because his bindings didn't fit his boots.