Bold statement there
But again, you have to see how rare it is for guys who don't produce in junior to become consistent offensive threats in the NHL. Even if Zacha's conversion rate is double the OHL average, he would still only end up a 45-50 point player. But that kind of conversion for a top prospect doesn't happen that often, as you are finding out.
Obviously stats are only part of the equation for a player like Zacha, who can bring so much more. But if he were a one dimensional scorer, I'd be very concerned about his ability to become an NHL player.
To compound this issue, historically scouts haven't been very good at accurately identifying what those other dimensions are in junior that will lead to success in the same dimensions in the NHL.
Most two-way NHL players had very significant offensive production in junior. Furthermore it is often the players tagged as "boom or bust" one dimensional scorers that end up becoming the best "value" players later in the draft (these players tend to excel at possession metrics in bottom six roles far more frequently then the projected "safe" guys do).
The concern becomes [the ability to "play good defensive hockey" in junior] /= [the ability to "play good defensive hockey" in the NHL]
One theory i hold (and the whole reason for starting the project i have) is that the minimum "thresholds" for performance/attributes to become an NHL player, even a bottom 6 grinder/plug, are generally above the same thresholds to be a strong offensive contributer in junior.
So to sort of arbitrarily put numbers on it EA style:
Essentially, in order to be an effective NHL player of any caliber, a player needs to have a skating speed of 80. If your at a 75, you simply will never keep up to the play.
But in junior, having a skating speed/rank of 80 is fast enough to generate points and opportunities off that speed alone.
Unfortunately i don't know how to test this theory beyond simply looking at junior scoring to NHL success, which has already shown to be a very strong predictor (relative to NHL scouting departments and third party scouting lists)