The "live demo" in the linked github doesn't seem to be very "live", in that it seems to be totally static. The post talks about "drawing correlations" but all it does it make a graph. http://sciview.herokuapp.com/#/data-sets/0
Telemetry, analytics, data visualization, and things like AB testing would probably work just as well for a dark web market as they would for Amazon. It's all about the money.
As for why they felt they needed to create their own specific tool for this specifically, I'm not sure.
And it takes less time and is safer to write the software yourself than to do a full code audit of any self-hosted solution. Plus that would usually involve business contracts, etc.
It wouldn't be very plausible even if this guy was a programmer, asked to make some generic analytics engine for a spaceship (because things rarely are truly completely generic). But this guy is a designer. You do not hire a designer, because drawing a picture for UI is some secret knowledge available only to them, but because it requires spending your time thinking about this specific problem and picking pretty colors. So if I wanted to make some app without telling designers about the real purpose of the app, I wouldn't really need a designer at all. I would hire a programmer and ask him to make me another Salesforce, with exactly the same GUI.
I'm not saying the whole story isn't BS, but at least it didn't claim what you assume it claimed.