I think there is some truth in it. Martial and Shaw have been imo unfairly treated compared to other older players. They would get dropped after performing averagely in 1 game, while players like Zlatan, Fellaini and Darmian after performing poorly in periods last season were not subsequently dropped for a sustained period like the other two. Rashford of course dispels this but I also feel like Mourinho, to a degree, was giving Marcus the game time to then counter the argument that he doesn't give youth a chance (literally just said it a few days back).