For me what fake means in BB is... Someone know the game and doing everything with some game plan and statergy but behaving like innocent and acting like don't know anything about game...
Initially Rio behaved like he is very casual with everyone and caring for everyone it's was clear he know the game very well and doing anything by thinking from audience point of view...
Now may be the contestants also realized about his Fake/Mask.
But not clear about why they gave mask to Aari.
Your definition of fake makes sense to me... but I notice that when someone in BB is being nice, people on social media are calling it fake.. I don't agree with that. Maybe yes, they are playing it up a few notches but maybe they are just trying to be friendly..
Rio - the caring part may be true (benefit of doubt is given) and he did say, he came to play the game. His advice to Anitha was good but yes, he is overdoing certain things that he may feel is pleasing to the audience. He needs to tone down those things..