The pitching moment is one factor. But the model would need to be very close to neutral stability for this to be a factor. Or, in some cases, the layout of the model is extreme.

The Slopoke is one such model. If set up with minimal positive pitch stability at it's normal speeds it has a wide enough chord and short enough tail moment that it can tuck just due to the poor aerodynamics of the design. I have not flown one but I would not be a bit surprised if the Clancy Lazy Bee is another model with this sort of poor behaviour if set up with the CG in a rearward but still stable, for the most part, manner.