Not necessarily, I tend to agree with him. Martial doesn't strike as someone who's giving 100% at all times. Maybe it's actually incorrect, but there is definitely a perception issue when it comes to him. The fact that he's lost his place for France is a bit telling as well, even if Deschamps is incomprehensible at times in his choices.
Also, he is correct, Martial should be someone who could score 20 in 20, he has that kind of talent and ability and showed it from the age of 19, but his progress has been lackluster. Sure, he deserves more playing time, and I feel Mourinho has been too difficult on him at times, but it's ultimately up to him to show progress and so far I don't feel he has made great strides in his personal development.