Proposal procedure is not something required to introduce a new tagging scheme, however, some people are brave enough to start it for tags they want to introduce. But then, they are not obligated to follow this procedure, not only in form of being able to abandon a proposal (which is normal - you don’t have to finish it if you don’t want to) but also in form of disregarding the RFC stage.
RFC stands for Request for Comments. Supposedly, it serves to collect feedback and to correct errors found by reviewers. But currently, proposal author is not obligated to take any feedback into account, even in a simple form of replies on a Talk: page (leave aside actual addressing the issues, mentioned there). Since voters are not always reading Talk: page, they could be unaware of those open issues and cast their votes regardless of that. This makes an RFC stage (and the whole proposal procedure) nothing more than a formality.
My view on it is that voting stage should never be started (allowed to start) without addressing every issue submitted by proposal reviewers. Otherwise, no improvement of proposed scheme is possible if an author is lazy enough.