To be honest, we should never actually believe in the data exchanges provide.
Many times the volume provided by exchanges are fake. After what Coinmarketcap did with the fake volume I have stopped trusting any of the sites and exchanges regarding volumes and marketcap and rather believe on my intuition on the trading aspect.
Coinmarket cap and other price tracking websites just give the value which are provided by the exchanges so you can't expect accuracy on it.
Anyway since coinmarket cap is acquired by binance, is there any considerable changes?