I think you've got it backwards. The stats I've seen is that the average NHL player has had his best scoring season by age 24 or so (keeping in mind that the statistics will be skewed by the fact that many, if not most, players wash out of the NHL by 24). It's usually the HHOF types who are the outliers, still putting up serious numbers late in their careers. So I think if you're going to look at stats of players with a 4-year career only, those are going to be their early years, so you'll see the top scoring age drop to 21-22.
But what I really mean more with Vilardi is that from my personal observations, it seems pretty rare for players, especially forwards, to have a solid NHL career if they're not already solid NHL players by 23. They just seem to get written off by that age and are rarely afforded the opportunity to earn an NHL spot, the teams always have younger prospects coming up who could potentially make a big impact right away. It happens, but I think it is pretty uncommon.