See, increase does not equal to proper forward projection of fees and volume. Not all of UNI would be accounted for in the first example, but I will not delve deeper there because nearly everybody agrees its not the optimal way to do things.
In order to do a solid analysis of the buyback programme, you´d have to analyse sell volume and buy volume for the entire day and then add on top of the buy volume the amount which would the money coming from the fee contribute. Saying the contribution would be low is just outright irresponsible without conducting a proper analysis with deeper meaning. Another factors which cannot be accounted for via a simple analysis are the psychological effects of the market participants: there might be a switch of behavior when it comes to the supply of UNI which is totally left out. Such superficial estimates do not even provide a raw estimate of the effect the buyback programme would have.