Let me ask you YES people my riddle again because it is the spirit of the original riddle. Depending on your answer will determine one of two things...

If a glider going 100MPH GS touches down on a treadmill going 100MPH GS in the opposite direction - does it stop instantly?

If you answer yes it will stop - then it is semantics and we are interpreting the original riddle differently. If you say no you are not understanding the concept.

Remember the original riddle does not concern itself with thrust. Only speed of plane. So the glider is completely appropriate and I think helps visualize the concept a little better