Players often use that stick push to help their teammate backcheck. Looks to me like Nylander dove not realizing it was his teammate and a very unfortunate result occured.
Diving for... what?
That's not hooking, it's not high sticking, it really resembles no penalty at all except spearing and Nylander was conclusively not speared directly in the butthole (a fact I think he would be keenly aware of in the moment) nor did he act as though he was speared in any way at all.
What's he diving for? What's the actual penalty and why do you think he thought he'd be awarded one?
And this is just occurring to me but above all else: why do we think a guy with a guaranteed roster spot is diving in the preseason instead of tripping and falling to the ground? It is quite clearly a more vulnerable position to be in, in a game nobody needs to win, so why is this what we're running with?