The ABC versus tiltrotor competition of the 70s used craft (XH-59 and XV-15) sized below what is being compared today (SB>1 and V-280). At the time, Sikorsky used to illustrate larger versions of the rotor system scaled to fit medium lift class aircraft, but as the technology proved toublesome from a vibration and flight control standpoint through testing, they were never put to task proving it was feasible.
Now that FBW and better AVC have addressed some of the shortcomings revealed 40 years ago, the elephant in the room remains the sizing.
Fundamentally, gimballed rotors used on tiltrotors don't have the same concerns with scaling, and whether or not that factored heavily into the JVX decision making process is debatable. That's not to say there aren't other tiltrotor designs that do not make dubious scalability claims - Karem's OSTR to wit. Yet more issues with a large rigid rotor concept, this time with the added challenge of tiltrotor dynamics. Karem seems to believe he can simply just tune high with some rather mythical ultralight and ultra stiff construction material.