I disagree [about the magnitude of the blocktrades account throwing off the entire dataset]
Okay, we disagree then. IMO when there is $40 million of slop it throws off most meaningful interpretations here. Yes we can say that such and such account sent or received $X worth of tokens to 'known' exchanges, but we can't really say how that compares with other accounts or the totals. If said account interacted with the blocktrades-related accounts (and/or other unidentified exchange accounts) in some manner we don't understand, it may be that the $X going to 'known' exchanges is very, very different from the amount going to actual (known and unknown) exchanges.
There is such a thing as error bounds, and the error bounds seem to be at least $40 million in magnitude. That is simply enormous relative to the flows going on here.
The data, as far as I know, does represent the sum of the daily net USD value of transactions to and from known exchange accounts. Any conclusions beyond that are up to others to figure out.
i would agree with that. Where we may disagree is how much additional interpretation is necessary to reach any sort of meaningful conclusions is required, or if it is even possible.
Without knowing the exact flow, it's hard to make your input actionable
It may in fact not be actionable. The Steem blockchain has a degree of transparency but as we have seen from the results, being your best effort and I'm sure a sincere one, not passing basic sanity checks, it is not clear there is sufficient transparency to reach meaningful conclusions. Or perhaps if some additional mysteries can be untangled the gap can be narrowed.