Yep. The hFov and vFov are limited by the driver itself, the structure of the headset internals - lenses & cup- and the so-called HAM -hidden area Mask. The driver and the HAM are software controlled, the structure of the lenses and the cup dimensions are hardware.
The designer of the headset decides the final FOV value, trying to match the hardware limits with the software limit to just render the visible pixels. So... again, the max hFov and vFov are normally fixed and can't be changed. There are other headsets like Pimax that can decide to alter programmatically the max FOV (Large o medium) by not rendering the pixels beyond certain software limits. But as far as I know, G2 is rendering exactly what the driver states.
Those with results above the driver max FOV values are using the pre-calibrated versions or a different app. ;)