The fact of the matter is (regardless of what people's versions of events are) they fought in the cage under MMA rules and were both willing participants. Harrop lost - that's a loss on his record. So unless anything else comes to light then that's how it should stand.
Oh and by the way, Katov is not a big welterweight but even if there was a weight discrepancy, they should have not fought and dealt with it there and then. They wouldn't have wanted it overturned to a NC if their man beat the Lithuanian dude with no fights (at the time) that they likely expected him to smash.