Useful?
As well as changing direction, I think some of the attraction is so that a plane or missile will overshoot.
It can also be used to put this plane behind the original chase plane.
Don't have the slightest idea how practical it is, but interviews with a couple of US fighter pilots said it could present real problems - I suppose that meant both having the other guy do it or having to figure that he could.
It would be terribly discouraging to be almost set up and find yourself in front of the bad guy.
Arf