This story is bogus.
Yes, the forensics is correct that at some point, files were copied at 22-mBps. But there's no evidence this was the point at Internet transfer out of the DNC.
One point might from one computer to another within the DNC. Indeed, as someone experienced doing this sort of hack, it's almost certain that at some point, such a copy happened. The computers you are able to hack into are rarely the computers that have the data you want. Instead, you have to copy the data from other computers to the hacked computer, and then exfiltrate the data out of the hacked computer.
Another point might have been from one computer to another within the hacker's own network, after the data was stolen. As a hacker, I can tell you that I frequently do this. Indeed, as this story points out, the timestamps of the file shows that the 22-mBps copy happened months after the hack was detected.
If the 22-mBps was the copy exfiltrating data, it might not have been from inside the DNC building, but from some cloud service, as this tweet points out. Hackers usually have "staging" servers in the cloud that can talk to other cloud serves at easily 10 times the 22-mBps, even around the world. I have staging servers that will do this, and indeed, have copied files at this data rate. If the DNC had that data or backups in the cloud, this would explain it.
My point is that while the forensic data-point is good, there's just a zillion ways of explaining it. It's silly to insist on only the one explanation that fits your pet theory.
As a side note, you can tell this already from the way the story is told. For example, rather than explain the evidence and let it stand on its own, the stories hype the credentials of those who believe the story, using the "appeal to authority" fallacy.