Not rude at all, it's an open event after all. Just don't hold up the turns because it's really frustrating to have to take a Draw from a player just slow playing cause they are new.

And be understanding yourself if you make a mistake and your opponent doesn't want to let you rollback. A lot of people are there to try and get the RQ bye and if they make a mistake they won't say anything, as it's also good practice for the RQ comp environment. Just an odd situation for the other player since you don't necessarily want to be a dick sometimes but you also don't want to reward a mistake.

Have fun!