I don't think that this is true. A snap roll is not an R/C only maneuver and has been around a very long time. I doubt that it was named after the sticks on an R/C transmitter.

A snap roll is an accelerated stall with a one revolution spin. I believe that a "true" snap roll is done with just elevator (possibly with some rudder to control the direction of the spin).

To get a true snap roll, you need enough elevator throw that you can change the angle of attack enough to stall the wing at high speed. In fact, one of the main symptoms of a plane with too much elevator throw is that it will do a snap roll at the top of a loop with no rudder or aileron input. When I set up a plane for aerobatics, I set up the low rate elevator throw so that it won't quite do the snap at the top of the loop, and then set the high rate high enough that I can snap the plane at any time with a full elevator pull.

That said, the control inputs that you listed will work great for most planes. If the original poster's plane won't snap using them, then it might be time to add a bit more elevator throw. Take care while doing this, that you keep the plane comfortable to control. Add a little bit of elevator at a time.

Thanks,
-Wade