Thanks for your help, you have explained it perfectly.
(Quoted from comments above):
The exception is only made for protected questions. You can ask questions, and answer unprotected questions, and even leave comments, but if you want to answer a protected question, you are expected to prove your mettle in other ways, first and foremost. – @J. M.
The association bonus is in order to let you have features like commenting and voting, because you obviously know how to do these things properly from other sites. But protection is meant to block unwanted "trivial" answers, and both "unwanted" and "trivial" are very subjective per community, so you are required to at least interact with the community in a positive manner before you are allowed to answer protected questions. – @Asaf Karagila