Well, Uncle Toni has been working with Felix on his claycourt game for at least a year year now, no?
Here's the thing: all this talk about how gifted Felix is, but compared to some of the other contenders for the post Big 3 throne at the moment things are not looking good for him. Granted Medvedev hates clay, but even he has had some good claycourt results in Masters and Majors. (SF at MC, QTRS at FO) Rublev has done well on both HC and red clay. Even the Crown Princes (Tsitsipas and Zverev) thrive on both and young Jannick Sinner has a Masters finals on HC AND a QTRS at the French Open. Ruud, more a claycourter had a breakthrough at the Miami Masters reaching the finals. Of course we all know how well Alcaraz has done on both surfaces.
So maybe Felix won't understandably beat Novak tomorrow, but if he's still a one surface wonder maybe it's time to reassess how much he'll climb. Though I do think at least making it to the QTRS here at Italy is potentially big for him.