I am seeing a lot of people do this.
Several answers come flooding in to a question, one of them is clearly correct, several are not or are missing vital information. Users who have posted these sub-par answers suddenly see the better one, and quickly make sure to change their answer to include a reworded version of the clearly better answer. Sometimes the new version is a little bit clearer or has an extra link in order to one-up the other user, but doesn't add anything relevant.
I encounter this frequently when 4-5 answers all show up at once, one is clearly right, sometimes straight up shaming the other answers, gets a couple immediate upvotes or a comment along the lines of "+1 for being right", and then suddenly one or more users with the bad answers totally revamp it to match the correct one, often within the "grace period" (how long is that?) where it will not be marked as edited. So all within a few minutes.
I know that the revision history is available to anyone interested, but it's unlikely to be scrutinized. The slippery slope here is that there's no proof - but sometimes it's really obvious.
What is the correct approach to dealing with this? Just let it be? Call them out politely?