I too agree with the real or perceived tow handling characteristics.

Looking at things from and aerodynamics standpoint (and I am about as
far from and aerodynamicist as you can get) it should seem that part
of the empirical data would suggest an experiment where you fly a
glider equipped with and Angel of Attack meter at your typical tow
speeds and record the AoA at various speeds. Then fly that glider on
tow at those same speeds and record the results.

I would suspect that we will find that the AoA is higher (e.g. closer
to the critical stall AoA ) and that this would explain the handling
characteristics. So the million dollar question is why? My guess is
that in soaring flight we are essentially coasting down hill at say
60Kt. In towing flight at 60Kt, we are being "dragged" up the hill
(plus, maybe, some effect from tow rope attachment point leverage) so
something, aerodynamically. has to be different and that has (???) to
be the AoA. As we all know from out stall training, as we approach
the critical angle of attack, we loose out roll (aileron)
effectiveness.

....or should I go back to learning to flip burgers at McD's?