I think that's absolutely true. Tolvanen definitely brings more than Sprong and fits better in terms of his overall game. I'd also agree that Donato is a better 4th line/role player fit as he does bring a little more of a 2 way game along with high effort.
As we grow/develop/evolve we have to look at individual roles more and one dimensional scorers don't really fit on what you want out of a 4th line. We need something more like the Vegas unit ideally.
Sprong is kind of similar to Olafsson in Buffalo. Another over 20 goal scorer who got moved to the edges of the line up to let the younger guys develop (Peterka, Quinn). The spots are there for Kartye, Wright, etc. to earn.