You could be right. That does not explain however, how you see Petan as a top line guy with the 1st line getting more playing time. I would be pressed to find a team where the top 3 lines get equal playing time. You also have to factor in that the 4th line is going to get tons of minutes as they have been the most dominant line in terms of how much time the play is in the other time's end. Also, defensively I feel so relaxed when they are out there because I trust that nothing bad will happen. I do not feel that way when any of the other lines are on the ice.
I don't see Petan as a top line guy, I see him as a complimentary piece to two top line players in Scheifele and Laine. Most coaches do not run a top line that consists of three legit first line players, they instead look for pairs and rotate complimentary pieces to fill out the slot.
Crosby and Getzel play with
Rust, Malkin and Kessel play with
Hagelin for instance
Mathews plays with Marleau and
Hyman/Ennis
McDavid plays with RNH and
Rattie
Ovie and Kunitzov play with
Wilson
Bolded are players who aren't top 6 talents.
Maurice operates differently then most coaches with regards to overloading his top line when he really doesn't need to and might be best served spreading his elite talent throughout the the line up like many other successful teams do. You know the saying "sometimes there are too many cooks in the kitchen" and in the case of hockey there is only one puck and play drivers want the puck.
The goal would be to to have two top line players on each of the first three lines:
Scheifele - Laine
Ehlers - Wheeler
Conner - Perrault*
Perrault being a quasi first line player.
As for teams with three lines running fairly equally see Tampa and Toronto this season, Pittsburgh three seasons ago when they won the cup.