I believe you are referring to XML tags in InDesign's structure panel, and not PDF accessibility tags.
XML tags follow the reading order of the content itself, not a chronological order. That's why it's call the structure tree of the document and not a timeline.
In XML, it doesn't matter whether a tag is the"Newest" or "Oldest."
So if you want a particular tag (and it's content) to appear at the beginning of the structure tree, then you must copy/paste the content at the beginning of the reading order. The tag should move with its content.