Yes the upvote and downvote buttons start a blue spinning wheel while it’s doing something, and then shows the updated vote count about a second later.

It doesn’t have to do with the phone. Probably it’s waiting for a response from the server before it registers the vote, and that takes a while.

Edit: For me the animation starts right when I click, it’s not delayed. Only the updated vote count is delayed. So maybe it’s not the same issue as you are describing.