as topic was started by spark users - did check what it crops from full sensor. then curiosity leads to check what air does.

but did not film FHD/120 at that time to compare, so anyone know it is same FOV as 30fps modes, or it changes?
(spark cropsize in link )

That might not be a bad thing.
Meaning it does not downscale the footage to get to 4K.
Downscaling typically means moiré and other ugly stuff.
The only thing you would wish is that they chose a native sensor resolution of 4K, so they did not have to crop for 4K
(giving slightly larger pixels = less noise as another benefit)