I played with a GFX at the Fuji booth at the Photo17 in Zürich yesterday, Friday 6th, and I can confirm that there isn't just a setting for a EFC but for an ES altogether:
Fuji have implemented a fully electronic shutter!
With that particular setting, the camera functions absolutely silently, any vibrations are totally absent.
As I wasn't able to use my own SD-Card to store the images, I cannot comment on any possibly negative impact on dynamic range when using the ES, like on the Sony A7RII.
Overall the camera worked very convincingly, the firmware seems well developped.
The menu is pretty much the same as with the X-T2 and the X-Pro2, but I only have very limited experience with those cameras.
They also had the first three lenses there, everything made a very good impression.
The rep told me shipping should start in march, no information about pricing yet.
Best
Jost