@Olivia I don't know about "supposed to", but the reviewer role isn't auto-granted with the current code. From what I've seen, moderators aren't programmatically given roles on MS. When I've seen a moderator sign up on MS, I've manually given them the Flagger and Reviewer roles, because,
as we say wrt. SD privileges, "we assume that moderators are, on the whole, pretty good at moderation." So, I've added the Reviewer role for Martijn.