I don't think people were saying Lavi developed FF. I think they were saying he has given him more confidence and a better chance to succeed by not demoting or scratching him based on 4-game pointless streak or a couple of bad turnovers or whatever the perceived error is.
I think Trotz is a more careful coach and one who is constantly making adjustments (or, to use his phrase, holding people accountable). He also prizes veteran savvy over rookie flash and energy. So i do wonder whether FF would have racked up same point total thus far under Trotz.
That said, there is more to our team than just the development of Bura. Overall, i couldn't be happier with Trotz. IMO, he is the best coach we've had in years, and we were damn lucky to get him. I was absolutely thrilled that we, not the Pens, landed him. He has our team on the right track. He projects strength and composure behind the bench. He has a ton of experience. He brought a very good staff with him, esp. the goalie coach.
Further, as good a job as Lavi has done with the Preds generally and FF in particular, I think he also walked into a very good, very stable situation with players who learned good habits under Trotz.