When I log in I always see a message at the upper right asking to please welcome our newest member.
I often did this until I realized that until they post 3 times they cannot send or receive messages.
Did I misunderstand the request?
Nope, it is a customary greeting to announce we do have a new member. True they might not get it until they have posted their five as per required. I think this is to ensure that they not a bot or a lurker or something. They may post later in the "Enrollment" section and you can officially welcome them then. If not you can always reply to one of their posts later.