My jet experience is exclusive to Boeings, but should apply to all swept wing jets (even though terminology might not match)
Ailerons are used to control wing roll. In this case of an engine failure they'll be the first control surface you use to stop any wing roll. On a swept wing jet, the rudder is (typically) the least used flight control in regular operations, so many pilots (especially pilots new to jets) are unfamiliar with the relationship between rudder and ailerons on those aircraft. Any asymmetry around the vertical axis will cause a rolling moment, since life is increasing on the forward moving wing and decreasing on the rearward moving wing. However, with an engine failed you have two choices, flying with the wheel slightly off or flying with the ball slightly out. This is for a few reasons, (1) on many types, the aileron-flight spoiler mixing is directly related to the angle of control wheel displacement, hence a neutral control wheel is desired; (2) neutral control wheel is equivalent to minimum drag, in an engine out climb (particularly after an MTOW takeoff) drag is not your friend; (3) full lateral control would be unavailable to the pilot if the aircraft is not flown with a neutral control wheel.
There is also a controllability factor to consider... if excessive left rudder is used, the aircraft yaws left causing the advancing right wing leading edge to be ‘longer’ (moving more directly into the relative wind) while the retreating left wing leading edge becomes ‘shorter’ (moving less directly into the relative wind). This excessive left yaw induces a left roll. If the pilot overcompensates with right right aileron, additional right roll is induced, and the cycle continues.