The tensioner pulls the belt taut when not in use, and the buckle drops down low, usually getting pushed into the cushion (or laying flat). So the center belt is out of the way. It actually is less annoying than the lap only belts--all of those that I've seen lack tensioners (at least in the center) and are otherwise flopping all over the place.
In my truck the front center is mounted onto the console which flips up for the center seat. Yeah, you'd have to be a midget (or ideally legless) to sit there. But it has a 3pt belt. Or at least I recall it having one, great, now I can't wait for lunch to go verify that...