are you in or out?

I don't know if this look is specific to the DC area, but last night strolling through Georgetown we saw a dude with his long-sleeve, button up shirt half tucked in.

By this I mean one side was tucked in, the rest of the shirt was hanging out.

Is this the new polo collar up?

Is this the "on the fence" of the corporate-casual set?

Does the side your shirt is untucked on signify where you hang?