inDesign document becomes "unsaved" after pdf export

just wondering if I'm going crazy or there's a legitimate reason for this. Whenever I pop open an inDesign document and export it to PDF, my document becomes "unsaved" as if I did changes to it.

However, all I did was Export. As far as I know, Export isn't supposed to change anything to the state of the document, no?

Should I re-save after an export? It's a bit of an annoyance, I often forget this happens and I always wonder if I accidentally moved a textbox or if it's just my export.

Thanks!