To add to OGB's reply, the vent tube runs to an inverted U that's about 12"-18" high, to keep fuel from leaking out. A straight horizontal tube over the edge of the tank could spill gas. The shop manual advises to avoid dips in any horizontal section to prevent fuel from puddling there, and horizontal section should drain back to the tank.

I had an engine fire once from leaked fuel, I try to cross the t's and dot the i's on fuel system work.