It's, at least, hyperbolic.
What's "all round productivity"? Shots and final passes? Do you think that receving the ball in a safe zone for the opposite team and carrying it to the edge of the box isn't productive? Does it just start to be "production" in the final third?
Salah is nowhere near Hazard in close control and making quick link up plays in tight spaces, things more related to AMs or even CMs, meanwhile the egyptian is much better at things related to forwards(pure pace, offensive off ball movement, etc). I don't even think that Hazard's shooting ability was inferior; he just didn't have as many opportunities to finish plays(for both: he had more responsabilities and wasn't as good at attacking without the ball).