Trending @Accenture; Letting client know about resignation

Can someone give any input in this please? If a person has recently been hardlocked into a new project where Accenture management is involved but he is directly working with the client daily. He has a Team Lead in client side who assigns tasks & gives KT. Now he resigned from Accenture within 2 weeks of joining the new project. The Accenture management is telling not to inform the client till last month of notice. So now client has no clue that all his efforts will need to be repeated for a new resource in 2-3 months. Is this person supposed to inform on his own to client or are we actually supposed to leave it to Accenture management to inform the client? Can someone give any input? Thanks!