That's standard for us. The 4 were also instructed not to cross the halfway line under any circumstances. That's fine, if that sort of thing floats your boat, all things being equal but not when you're one down in a tie.
Watch the last couple of minutes of the first half. Their defenders are knocking it between them. Kane is making a token effort to chase the ball knowing he'd be better off with his mickey in his hand and the Milan players are wondering how long they'll get away with it before Son and Kulu cross the halfway line which they never do.
fudging stupid, negative tactics in a game like that. Its not even the tactic, its the rigidity of it that the players can't deviate from it when it's making no sense right in front of their eyes.