There will be differences between the wings - nothing is manufactured perfect, flies do not die symmetrically on each wing (particularly given that the propwash is asymmetrically), the odds of managing exactly zero sideslip is roughly zero, lateral CG won't be exactly central, and there may also be a bit of asymmetry in the tail.
There are different types of stall, but if:
(1) The stall is marked by mainplane flow separation, and
(2) One wing, due to the asymmetries above stalls a significant time before the other, and
(3) The flow separation starts near the tip (rather than near the root).
Then you are likely to get wing drop at the stall.
G