A wide turn can be thought of as a FWD2 and a turn executed at the same time.
Consider the following example:
The robot, making a wide left turn, will hit the wall immediately, but continue to rotate and move. It will manage to rotate 90 degrees to the left, but it will only get to this position:
Much the same thing would happen if there was a wall perpendicular to the robot's orientation in the left-hand column; the robot would catch on its edge, and be stuck there until it had rotated enough to get past it.
In the case where there's a wall parallel to the robot's original orientation:
This robot is making a wide right turn. It will move north some, but turns until it encounters the wall.
The last case is when there are two walls interfering with the robot's movement.
If the two walls are adjacent to the robot's starting square, it obviously can't move. The robot will simply turn.
If the two walls are adjacent to the robot's target square, the one perpendicular to the robot's original orientation takes precedence.
This robot, making a wide right turn, ends up here: