Ask HN: Is there any downside to re-signing equity paperwork later?

Just got a bit of an unusual message from a startup I just left. I had just signed paperwork giving me equity in the company - since I was leaving, this didn’t need to vest and was effectively a straight purchase.

Now, a few days later, they want me to sign again with today’s date instead. They just closed a round right after I signed. Is there any downside to signing this?

The only issue I can think of is some kind of rights/preferences awarded to earlier shareholders over the new investors of the new round (who invested slightly later) but Google doesn’t turn up anything indicating that would be a consideration.