The playerbase isn't going to slowly bring his wr% up, if anything it goes down as effigy's become easier to spot.
The latter point is definitely valid and was a possibility we considered pre-ship, but early data has indicated that's unlikely at this point.
The other thing to think about is that even though there might not be as much to learn on this VGU as there is on a new champ, considering the amount of people playing him now vs. pre-rework, he might as well be a new champion for a lot of them. There's a lot of knowledge soak you can take in on how Fiddle is supposed to play that doesn't exist for new champs, which is worth something because I don't expect his playstyle has changed all that much, but we're still seeing the early WR climb we'd expect on any new champ.