I don't find the wording in the RFC to be that ambiguous actually.
> The answer to the query, possibly preface by one or more CNAME RRs that specify aliases encountered on the way to an answer.
The "possibly preface" (sic!) to me is obviously to be understood as "if there are any CNAME RRs, the answer to the query is to be prefaced by those CNAME RRs" and not "you can preface the query with the CNAME RRs or you can place them wherever you want".
> The answer to the query, possibly preface by one or more CNAME RRs that specify aliases encountered on the way to an answer.
The "possibly preface" (sic!) to me is obviously to be understood as "if there are any CNAME RRs, the answer to the query is to be prefaced by those CNAME RRs" and not "you can preface the query with the CNAME RRs or you can place them wherever you want".