In fact, he did exactly what you said can't be done. He had some help
from the main gear, which touched the runway several times assiting
his skidding turn. If memory serves, he wound up pretty much where he
started, pointing in the opposite direction. There were many, many
witnesses. What parts I didn't see while running, I had recounted to
me in excrutiating detail, mainly because it was my glider. (The pilot
of the 20F, by the way, nearly hit my other glider, a parked Pegase.
The only two French gliders on the airport. Proof again that like
seeks like.)

Better, I think, to start with observed facts rather than to try to
deduce them.

As for owning two French gliders, you are welcome to exercise your
powers of induction.