It's the exchange platform that has control over order book and trading volume so they are the ones who manipulate it.
Why you might ask? simply to become more visible in Coinmarketcap and also popular. Being popular means the exchange could charge more money to list coins and also means potential new users.
He might have a point on when the developers are the ones matching theirbown Bids and Asks in the crypto exchange. This is possible if they are also the only ones participating in that trade. It's similar to crypto exchanges faling the volume but the guilty ones here are the developera itself. You cannot really trust every data you see online as they can easily be faled to manipulate people, that is why if you don't want to be victims of fake volume you should always stay away from unreputable exchanges.