I think "interpolation" is not quite the right word here. The idea with these 48 MP sensors is that they group equally-coloured pixels in bunches of four, and usually average over these four neighbors to yield a 12 MP image. This is called "pixel binning" and reduces noise through the averaging operation.
Technically, in optimum light conditions, the camera could indeed record all pixels individually to yield a 48 MP image. But, seemingly, the Pro1X's drivers do not support that mode.
As @EskeRahn and @daniele606 point out, CPU-Z is wrong. Other apps correctly identify the SoC as