Some people (myself included) read that as "would ideally come first, but it is not neccessary that it comes first". The language is not clear IMHO and could be worded better.
I.e. the possibly logically applies to the entire phrase, not just a part of it.
- The answer - to the query - possibly - CNAME RRs - prefaced by - one or more - that specify aliases - encountered on the way to an answer
It might be a victim of polite/ironic/sarcastic influences to language that turns innocuous words into contronyms