Can a "duplicate" predate its twin?

You can argue about etymology, logic, precise definitions in dictionaries, etc., but at the end of the day a word can obviously be used the way people use it. Take:

I went through my stamp album and removed a few duplicates

You wouldn't normally assume I cared about making sure I kept the oldest one of each duplicated stamp. Anyway, I could proffer two stamps, saying These are duplicates. Which one do you want? Certainly no-one would study the date franks and say That's the original, and this is the duplicate!

In case it's not obvious, duplicate has two closely-related senses - is the same as, and is a copy of.

I don't suppose anyone has ever deliberately copied an existing query (verbatim, paraphrased, or whatever) on SO just so they could see whether and how quickly it got closed as a duplicate. Hence it stands to reason in such contexts it's same, not copy. The idea that the later one must always be labelled as the offending "duplicate" just comes from woolly thinking that could make us drag in concepts of credit for being "first".