This was a very good read thank you.
The author highlights his key strength as being a transition player and flat out says he is too raw/weak in the other aspects of being a CM, which is not good enough for a top team. His short passing, possession play, tackles and interceptions are no where near the top level. This is done by a much better statistical analysis than what I did
To your point about Brescia's passing as a team. Even if you relativize his numbers down to brescia's numbers. Only 10% of Brescia's passing goes through him (52nd percentile) compared to Pirlo who was > 90th percentile. Everything goes through Pirlo on Pirlo's teams. Tonali is just one amongst many players to his Brescia team mates. Unless their coach is an idiot, you'd think if he had a great passer who is head and shoulders above the rest of his team mates, they'd have used him more often as connector and playmaker and Brescia wouldnt be one of the worst teams with the ball in the league.
I think Mourinho would love a player like him for those park the bus games against bigger clubs. He has to improve on his weaknesses and Brescia's tactics will no doubt adapt to his new-found strengths if he becomes that good at them. Otherwise he'd be destined for mid-table/small clubs that like to take points off of the top 4/6.