You are right, we don't really know these numbers but if companies are releasing reports every quarter about numbers we might have a better understanding. Just like any sort of set of data we are able to analyze it overtime and watch for any major change that looks suspicious. I don't really know what their technology looks like on the backend but I would assume you are able to see the dust but what is more important and alarming are the movements of money that affect people.
But in this case though, it looks like it was just a individual, not a company so I don't think that anyone will oblige in reporting how you obtain your bitcoins. What if the individual users mixing services? Will CipherTrace really dig on that individual's history? And for the sake of argument, I'm also not agreeing on companies submitting any reports whatsoever, that's why we are decentralized and with ho higher authority to tell us what to do. Everything can be seen in blockchain, and then we have OTC trading as well. So it's really difficult to trace and follow every footprints here.
I am pretty sure AML companies like Ciphertrace are able to track the movement of funds even if they use mixing services. They do live demos of their tech so it would be interesting to see it happen in real time