It should use the same motor overload functionality whether it has auto up/down or not. How else would it know when the window had reached the top or bottom when you just hold the switch until the windows is fully open/closed? Another thing this does is prevent broken glass.
Even the cheap power windows ($145 for both) I'm putting in my 1934 Ford pickup will stop when it hits an obstruction regardless of whether it is auto or you are holding the switch.
You should be able to hold the switch and monitor the circuit to see what happens when the window reaches the top or bottom.
You might be able to put something that approximates an arm (tennis ball?) in the window path then use the auto up to see what happens.
WARNING: I AM NOT RESPONSIBLE FOR BROKEN GLASS IF YOU TRY THIS METHOD!!! 