It depends on the player.
Chris Kreider legitimately went from shooting about 11, 12% in the first half of his career to shooting 15% on a bad day.
A guy like Reinhart, who is entering his prime, may have legitimately developed his game to finish better. Granted, he's shooting 25% this year, but like, he's not gonna just be a 60 goal guy now. It's just a career high and there's nothing really of note there. Every player has a standout year or two in either direciton.
That being said, Reinhart is shooting almost 19% as a Panther over 228 games. I could see him settling in at 17% and legitimately being a 40 goal guy for the next few years.