It's different on the 48MP Quad Bayer iPhone sensor:
Instead of something like RGBRGBRGB for the subpixels the subpixels are layed out as RRGGBBRRGGBB (in both dimensions). So while those additional subpixels provide some additional information (either brightness information or a different exposure time for HDR) in terms of color information the sensor would still be pretty much limited to 12MP. Based on the reviews that I read in the past Quad Bayer sensors seem marginally better than comparable regular sensors (48MP Quad Bayer vs 12MP regular), but nowhere near as good as the MP number makes them look like.
Instead of something like RGBRGBRGB for the subpixels the subpixels are layed out as RRGGBBRRGGBB (in both dimensions). So while those additional subpixels provide some additional information (either brightness information or a different exposure time for HDR) in terms of color information the sensor would still be pretty much limited to 12MP. Based on the reviews that I read in the past Quad Bayer sensors seem marginally better than comparable regular sensors (48MP Quad Bayer vs 12MP regular), but nowhere near as good as the MP number makes them look like.