No one can accurately determine whether the data provided by the platforms are accurate because they are simply not subject to independent institutions exercising some sort of regulatory authority.
The best we can compare is the trading volumes on platforms that fiat money pairs such as the dollar, euro, and others.
For platforms dealing with cryptocurrencies, it is difficult to determine the accuracy of volumes based on the report provided by the platform.
If for anything, I'm sure the volumes on exchanges like Binance, Okex, Houbi are legit. Only small small exchanges will opt for faking volumes. I remember Hotbit and CoinOne faking volumes at some points between 2018 and 2019. Coinmarketcap.com actually has a filter
"Adjusted volume" . They say It reports the actual volume, different from the one reported by exchanges. I'm not sure about it though.
i think "Adjusted volume" not say anything . people now lost trust in CMC