An ETF will only calculate the larger institutional capital investments that are done on a daily basis and will not include the millions of smaller transactions that are done by individual on 1000s of exchanges all over the world. Also remember that CMC are only using transaction data from the larger exchanges out there and most of the transactions on the smaller exchanges are not even counted.
Also look at the motives for Bitwise to do this research, to find the hidden agenda for this revelation.