When you take a photo on iPhone, the image is composed of up to 128 frames taken before and after you hit the shutter button. Those frames are aligned and stacked using dedicated image processing silicon which can do that stuff reasonably power efficiently while working at those data rates.

The stacking also allows things in the frame to move - it uses optical flow to track movement.

That's how iPhone manages to take a tiny very noisy sensor and give non-noisy output.

If you want to see how the camera performs without this stacking, try taking a photo from a moving car of something behind railings. The moving railings screw up the optical flow, so most of the 127 other frames will be discarded (if regions of an image arent a close enough match, then the region will be discarded), and you'll get to see all the sensor noise.

Sure I know, GCam pioneered this years ago. But all those frames are merged into one which is written as a correct scene-referred DNG with the usual dimensions and the CFA pattern, as if it was taken by the sensor directly. Which is what GCam and every other app do. They don't write gigabytes of RAWs for a single shot. (although some apps do have that option, within the hardware capabilities)

And all this has nothing to do with manual astrophotography, where you ditch computational apps, use a mount and shoot actual unstacked raw sensor frames with several seconds exposure each, interleaving them with dark frames, and do the computation yourself with the dedicated astrophoto software which is far better than any app if you calibrate the sequence and do the math correctly. Every phone is capable of this.