I have noticed this happening on several occasions. One example:
The OP goes ahead and marks several related questions as duplicates:
I know that marking older questions as duplicates of newer ones can happen (although it is somewhat counter-intuitive since one cannot duplicate something from the future). This is something exceptional since it is harder for the new question to gather better answers than the old one which had more time to get well developed answers.
I think the more appropriate way is to put a comment or update the original question, if it is close enough. Also, marking several older questions as duplicates (others than the duplicate cause) does not seem nice.
Question: How to deal with a question closed as duplicate when the OP marks several old questions as duplicates?