Yes, well I thought this too, but then I saw a number of publications saying if you wanted them to publish an existing story, you had to deleted it first and submit to them as a draft. Then I saw a story addressing exactly this issue: https://medium.com/feedium/yes-its-ok-to-republish-old-stories-on-medium-to-get-a-newer-publishing-date-87d3b6926182. I've done it occasionally, but always tried to improve my story first, so it's not been exactly the same.