All single-sensors cameras are like this.
Each of the R-G-B sensitive photoreceptors in single-chip sensors are arranged using a Bayer filter pattern which looks like a mosaic. The filter pattern is 50% green, 25% red and 25% blue.
The "pixels" of the final image needs to be calculated from this pattern (called de-mosaicing or de-bayering). There is not a 1-to-1 correlation between RGB pixels in the sensor and RBG pixels in the final image, and the final image size may depend on different algorithms to remove artefacts caused by the filter.