Games installed on an XBox One
I'm looking at buying a second-hand XBox One for my son. Somebody selling one has a couple of games in cases to go with the box. They have also said that they have two games already installed on the box. Surely, if I buy the XBox off of them, won't the installed games be registered to their account? Would my son still be able to play the installed games if he does not have the games in their cases? Thank you.