totally wrong
in a fully developed spin in a c150/152 just letting go of the controls WILL NOT result in recovery. in a fully developed spin in the baby cessnas, if you just release the controls they will remain in the position where u released them. ie: stick still full back and rudder fully in. THEY WILL NOT CENTRALISE THEMSELVES. most instructors have only experienced the developing spin. this is the condition where, yes, if you release the controls they will centre and the aircraft will pretty much recover by itself, albeit in a very nose low attitude. it is not a fully developed spin.
i have seen many instructors sh.it themselves when the little baby wont recover by itself. the beauty of the fully developed spin in a baby cessna is that its fairly hard to get the aircraft to do it. and you need about 8000to do it safely. the ugly side is that it does not recover instantly, and can take up to 4 complete revolutions for the recovery to even start to work. all the primary controls are very very sluggish. unless full stick forward is held, and i mean held, the aircraft will not recover.
its very exciting, and a lot of fun. but you really have to be very careful and have heaps of insurance.(altitude).