Yes, the admin was me. The round before we had 2 players using variants of the name Player which were not easily discernible from one another. One of them team switched, which upset many players and even caused one player to quit. I could not tell which one of them switched because unfortunately, I did not take the extra steps necessary for me to track players other than by player name beforehand.
The next round a 3rd variant of Player joined and I asked the 2 that had deceptive substitutions to change their names. [Edit: Correction, I had to quit for a bit after the round described above and came back later and it was then that noticed there were 3 "Player" players and not the "next" round.]
The purpose of that rule is to make sure individual players and their names can be easily identified.
I have oft wondered if it would be much easier to manage the server if you had a rule.... once you have a player name, you must use that name. Admins would be the exception so they can discreetly police the server.