It's because that's where the primary restriction area is: new members cannot post, and then they will try to post anywhere. It is meant to help alleviate all the scams and protect LRH members. I agree that it could be more clearly stated, but it has always been there, and it is associated with a new member not being able to DM or receive for the same reason.
Here are a couple of threads from the Website and Forum Support section that address the issue with the Admin's input.
https://www.longrangehunting.com/threads/still-unable-to-pm-people.352461/
https://www.longrangehunting.com/threads/insufficient-privileges.347778/
