But, again, being about to outmaneuver a starfighter doesn't make your ship a starfighter.At Endor the Falcon is shown engaging, outmanoeuvring and chasing down TIE/INs. That suggests to me that from what is shown in RotJ the Falcon in X-Wing is working in line with the lore.
The Falcon is a cargo ship. It's a very maneuverable and well armed cargo ship, but it's still a cargo ship.
Extensive mods have turned the Flacon into a gunship more than anything by ROTJ. Before then it was still possible to think of her as a modified freighter/transport mainly used for smuggling or blockade running. Never a starfighter (even if you include the heavy assault ships like ARC-170 as starfighters).