ATCs along the way don't necessarily need to get the full picture. Each one is responsible for a zone. They have planes about to enter their zone, they route them/land them and then the plane moves out. Not saying they can't easily get the flight plan and figure it out, but they probably wouldn't normally do it.
But no matter how small the zone is, the point where the plane is to make a 90/180/270 degree turn is only in one zone. That means the ATC responsible for that zone would see it. Are normal planes really doing 90 degree turns?
