With current sensor technology in nearly all cases (a few rare counter-examples now exist) it is nearly impossible to do what you are suggesting. The issue is the time it takes to get data off the sensor into the buffer and compressed. The sensors in the phones can not be read all at once, they have to be read one line at a time. This takes time, per line. Second, the more data, the more work it is to compress. So the solution to both problems at once is to take fewer lines, skipping every X lines on the sensor to get something close to or exactly 1920xwhatever width. Well guess what? This is done on hardware and cannot be switched in direction. The hardware is designed with readouts in one direction only.
So no, sorry, it's not a trivial matter of engineering, it's actually a very non-trivial matter to get this working at all in the first place, especially on such low powered, low cost devices.
Now, there are some sensors that can do global shutter, full read-out and these are used in higher end dedicated devices for high quality 4k recording and such, but, the hardware isn't even remotely close to fitting in a phone.
So don't expect this kind of behavior to change any time soon.