Robert M. Gary wrote:

I think you are stretching the FARs a bit. Are you saying you think its
ok to give instruction when there are dual controls but the instructor
can't access them?

yes. That said I don't think it mattered in this case -- the instructor
most probably didn't log (past a few tens of thousands of hours) and
the flight didn't have to be an instruction flight.

91.109
(a) No person may operate a civil aircraft (except a manned free
balloon) that is being used for flight instruction unless that aircraft
has fully functioning dual controls. ...

there is more to it than the intro you just quoted.

--Sylvain