That's because he knows what he's talking about. It's not an assumption.
Maybe there is a sport that will make it easier for you to understand.... If a batter lays down a bunt, and then runs to 3rd base. What you are saying is, "How do you know that's not what the manager has been teaching him to do"?
Nothing about Kane's movement/spacing on that play was correct. Under any system, coaching, or guidance (to be fair, Kane is not a D... but he was playing one).
Which is why I said earlier any d-man or the other listed Sabre forwards I named would have sealed Tarasenko to the boards.
@those who think blame was on Eichel, or shared 50/50 with Kane, do you think Risto heads up ice if he & Kane were switched sides? Do you think any other Sabre d-man or forward would have abandoned the puck-carrier's side of the ice and headed up ice to cover a Blue not yet to the red line?
Doesn't matter whether it's 5-on-5, 5-on-4, 4-on-4, 4-on-3, 3-on-3, when you are the last man back, facing the puck carrier, you play the puck carrier and let the lesser threats go.
For those hypothesizing Kane was "thinking" and waiting to pounce on a poached puck / Eichel takeaway: Isn't the higher percentage play for Kane to wall-off Tarasenko by moving laterally, and let Eichel either retrieve a dump-in to the Sabre zone, or hook left to recover the puck / break up a pass?