My understanding is that the in-camera Fuji simulations bake in other features that software to date does not. Some understanding of the particular grain of these stocks for example or the particular way highlights fall off. i.e. something that a slider or popup menu isn't going to deliver. I have found that the approximations to these in Capture One have not matched what the camera puts out.
I wonder if by tethering, they can harness that intelligence and whatever juju they've put in their camera bodies, and apply it to Fuji RAF files that exist on an attached computer, keeping one of their key selling points protected perhaps.
Using a 3" screen is indeed sub-optimal, and I for one would value being able to run through the simulations on a larger color-corrected monitor.