"Paul Lynch" wrote
That cite works for a student pilot. A certificated airplane pilot getting
glider training is not a student pilot.

Correct, and precisely my point.

As another poster noted, a CFI gives authorizations and may limit them as he
or she sees fit. Operate outside that authorization and you violate Part 61
and possible Part 91.

Really? Exactly what part of Part 61 or 91 will you be violating if
you are not a student pilot? Chapter and verse please.

Michael