The Falcon really isn't that far off, the exterior just needed to be about 30 percent bigger for that interior to fit.
. . . or the exterior & interior each could have moved by 15% to meet in the middle.
Movie shoots will enlarge interior sets for shooting access just as often as they shrink exterior sets for soundstage room.
Even the MF's big interior sets were noticeably smaller than the original ILM model implied. And GL wasn't happy when Gary Kurtz had the ESB cockpit enlarged a bit. GL never wanted that ship too big & comfy.