Because Pogba/Mourinho issues started due to criticism in public ? Mourinho has been very defensive for him in the pressers ever since the first season.
The issues started when Mourinho told Pogba to do certain role in Spurs game at Wembley, Pogba neglected it and was subbed few minutes later, then started to get dropped from selection later on.
So yeah the statement is right, if another player did the same with Fergie, he would have been chopped off in summer immediately. Mourinho has been in fact too patient with Pogba if anything else. The one who was bitching in the media this far is actually Pogba not his manager.
Criticism in public can be applied on Martial or Shaw but definitely not Pogba.