I have read that in adjusting cup and cone hubs you should leave a small amount of play which will then be taken up by the clamping action of the quick release.

I cannot subscribe to this as each cone is fixed in place by a lock nut and therefore cannot move.

Is this just another old wives tale or is there genuine engineering evidence to support this idea.

I doubt if there is but am willing to listen to those older and/or wiser.