This is, in practical terms, a bigger version of a one-way mail slot. I fail to see how it would be a 'defense' or 'trap', and indeed a major part of the point

This is, in practical terms, a bigger version of a one-way mail slot. I fail to see how it would be a 'defense' or 'trap', and indeed a major part of the point of authenticating drones would be to avoid the problems that could come with accidentally trapping small animals with a much simpler one-way spring mechanism.