Can you share where you are seeing some of this information?
I took a search on footystats and found high level comparisons interesting between the two leagues:
https://footystats.org/italy/serie-a#
https://footystats.org/england/premier-league#
2.57 goals per game in Serie A vs 2.85 in Premier League. I don't think the absolute #goals point has much legs personally. City and Arsenal might be skewing the stats with their rampant performances and I'm curious to know how comparable the goals scored is among the mid table / relegation belly of the league.
Atalanta scored 66 goals whereas we only scored 58. But looking against the rest of the teams, I don't see a material difference. I think we probably score slightly more across the board because of the style of play being more attacking minded, and yes that builds well for strikers, but I don't think that positive landscape for strikers outweighs the negative in a quality jump required for Hojlund to hit the ground running for us.
Also I have to caveat my cynical opinion of him is based on the videos I've seen. He isn't as clean in his general play and his arial stats for a player of his height looked bang average. We can look at Darwin last season (who came in with much more impressive stats) to see how this league can eat a player up if they aren't ready.