According to Osho, yes—masters yawn, but wholly. The hallmark of enlightenment is totality: whatever happens—eating, walking, sleeping, yawning—occurs without inner division or a separate doer. Ordinary people act partially, with a controller holding back; a Master disappears into the act. In a Master’s yawn there is only yawning—pure, undivided presence.
Masters do yawn, but unlike us they let it happen completely, with their whole being, without holding back or trying to control it.