It actually stands to reason; people often find after they publish a poll that they could have worded a question or option better, then try, then discover that the meaning of the question or option now takes on a new defining intent - that's unacceptable manipulation, whether intentional or not.
When you start a DM, #Mitra won't let you add/remove addressees; last time I checked, mastodon will - it shouldn't that's a potential breech of privacy & security.