Not sure what exactly is a 'zone start differential', but Larsson doesn't have the best Corsi numbers on the team. In fact, he's got one of the worst individual Corsi numbers on the team. He's ranked 19th out of 24, to be exact. And it shows how non-contributing he's been offensively. He's recorded 1 point in 18 NHL games so far. That's not NHL-ready by my book.
His team Corsi (meaning the number of successful Corsi actions when he's on the ice) is very good indeed. But so is D'Agostini's, *Adam's*, Girgensons's, etc.
If you mean that he's ready to be a 4th/3rd-line grinder, I guess most people would agree. But I don't think that's what you meant by comparing him to Hecht, who was a 50-60 point guy at his peak.
He starts ozone 40% and finishes ozone 50%... It's an very high rate and indicative of quality possession