Yes, but it would be very harmful to them. Traders using their site would be able to see that something was going on very quickly. Also the fact that their volume literally went up 50000% in a day makes it unlikely that this was some kind of "clever ruse."

What seems most likely to me is that a combination of lowered trading fees and an incentive program they just launched allowed someone to trade for free or make a rebate on otherwise unprofitable trades, and they decided to exploit this until it was noticed.

We won't know until the site op posts an update.