I'm not sure why Maguire pointing as Kane is being taken as him specifically telling Shaw to go to him. Players point to opposition players in space all the time, and any of Pogba, Greenwood or even Matic would have been better options to be trying to get there to cover him.
Maguire did plenty of things wrong thoughout that entire play, but pointing to Kane wasn't one of them. On the other hand Shaw didn't do anything else wrong throughout the play, but then made the one big mistake of charging out at the end.