They self-correct, by aerodynamic means, for minor perturbations in the atmosphere. They do NOT correct for wind direction and vertical perturbations.
If a thermal bump raises a wing, the aircraft turns away from the high wing, re-entering the thermal what is basically a 270 degree turn. An autonomous vehicle would correct for the high wing through a control deflection. (yes, it has been tried with pendulums-a rudimentary autopilot). That is not autonomous control--that is the key word, "control". The DT system and engine cut-off are not true controls- they are limits. Even the Bunt system is limited in scope, and does nothing to control the flight after initiation.
from the engineering point of view, autonomous means active control. The flight of a Free flight Model is NOT an actively controlled flight.