It is possible to clear the blocking ball ball when the cue ball is about a chalk's width to half a chalk's width apart from the blocking ball at less than a 90 degree angle approach on the cueball. There is no chance that the shaft is causing the forward motion on this shot. So I think that it's possible that the forward motion is not from the shaft on the 1mm jump. In any case it faster than the eye can see and so it's "legal" 
