The greatest concern of ALL relay team’s at any level is “to get the baton around.” The idea the baton will be exchanged before the zone seldom an issue. Hell athletes are probably not even aware of the line that indicates the beginning of the zone but you can be certain they know where the zone ends.
I don’t believe Doc was wrong for putting his hand back as all he did is do what he’s suppose to do when the assigned verbal cue is given. Shawn, on the otherhand, should have ran behind DP until they were safely in the zone. But again their one and only concern was to “get the batton around.”