I've taken several Realforces apart. I remember the switch housing for the Ctrl key being somewhat different than the rest. The plunger is maybe a little smaller and doesn't have these two tabs that prevent it from falling all the way through if you remove the PCB from underneath it. I also remember it being the only switch on the board that had some lube on it.
I don't know why they decided to make the Ctrl key different than the rest, but it's definitely not a defect, it's designed to be that way. If it really bothers you, can take it apart and swap the switch housing with another key on the board.