Offline
As a designed play, especially with a tall WR. When a DB doesn't see the ball coming he can get really out of position. With good timing between QB and WR, I could see this concept being relatively high percentage.
I know they (QB's) have purposely done that (underthrow the pass) for years, but I don't recall the exact scenarios that call for it.
(I'm thinking single DB in man-to-man in tight coverage, but, again, not sure. Advantage goes to the WR for finding and catching the ball.)