Obviously the tactic couldn't conceal the soldiers once they came within a certain distance of the castle, but how much extra time could such a camouflage be expected to give to an advancing army, if the tactic was ever successfully pulled off?
Jacob Grimm suggested that this motif in Shakespeare's Scottish Play is based on a folk legend, itself inspired by the cutting of tree boughs for the May Day march of the young men into a village. See this source for example. I know you are not asking about the origin of the motif - but this evidence suggests that there may not have been an actual expression of this strategy on the battlefield. It is a dramatic, but not very effective motif
Not an answer, but a sort of clarification of the question; I've always been under the impression that Macbeth is set in the relatively distant past - 10th century maybe (not as far back as Lear, but not as recent as the Richard II)?
I mention this because it may be relevant to the answer, if there was in fact such a tactic in that time period but not in the 16th century.