I wonder whether there's also a positive aspect to the general well-being of the nucs if they've got a few drones onboard (even if that means adding select drones from chosen lines)? It certainly mimics, better, the real life of the bee and ultimately I think that's what we should be doing.
That said, exclusion of energetic burly drones, determined to get out, might be a positive thing if the boxes are going to be stored for any length of time before release...