Prototypes and RFC can go hand in hand or RFC can be later in the process. I don't think it's either/or choice. The example problem author gives is that someone

Prototypes and RFC can go hand in hand or RFC can be later in the process. I don't think it's either/or choice. The example problem author gives is that someone built something but hasn't communicated across the team. As he points out the list of issues, consensus is the least (3rd - "Someone made an important decision on behalf of our entire team, but the team wasn’t included in it") of the worries. As someone pointed out in the thread it is "Request for Comments" and not consensus. It is fine even if comments are ignored by the author. It is never fun having to find out something has changed only after production release or later down the line.