It was 70% of the trading done on -unregulated- exchanges.
You don't ask for btc price X on coinbase versus btc price Y on biance? Wouldn't you just care about the price of btc? and if it rises on certain exchanges, then it would arbitrage until it rose on other exchanges as well?
More like the opposite. The fake price rise would be arbitraged away to match the real price.
At some point there has to be a real buyer/seller, otherwise arbitrage doesn't work. And a real buyer/seller is trading at the real price.