Actual barrel slide separation takes place fractions of a second after rearward
movement of both,this is the critical point.
Yes. Separation occurs after the lugs have vertically disengaged. A timed event that occurs at its assigned place in the cycle...regardless of the speed of the cycle. Firing normally or in slow-motion by hand...the barrel begins linkdown at .100 inch, and it's completed at .250 inch of travel.
While the lugs are still vertically engaged, the slide and barrel can't separate.
Which incidentally, is why the pistol can't fire far enough out of battery to kaboom. At .100 inch out, the hammer can't reach the firing pin...so even if it could fire that far out...the lugs are still engaged and the breech can't open.