I would hazard a guess in practically all swept wing airliners that the use of large deflections of rudder at slow speeds (high alpha) would create rolling moments that could exceed the power of the ailerons to counter.
This would be because of the large slip angles that can be generated at low speed and the effect slip has on on the swept wings creates a large differential in wing lift that could not be corrected with full aileron.
The effect of any wing dihedral might exacerbate the rolling moment?
Hey, but I am only a pilot...we require an Aerodynamicist armed with theory and graphs to chip in!