Kane was excellent on the walls, very hard to knock off the puck. He didn't engage in contact, but contact didn't keep him off the puck the way it does with many softer forwards.
He also proved time, and time, and time again that he could rip seams through the best defenses the NHL had to offer during the toughest games. When I think of "soft" it's not just about hits, it's about how easy a player is to shut down. Guys like Marner are easy to take off their game even when they have better players around them.