Cameras should have just rotated the actual image pixels when saving, instead of cheating. If that's too slow, implement it in hardware, or schedule a deferred process and don't let the images be exported until that's done.
No, it was an elegant hack given all the constraints which mostly no longer exist on modern hardware (although I wouldn't be so sure about really small embedded systems).
Sure, modern cameras will have no issues loading the full JPEG into memory, but how would you have implemented this in cameras that only have enough for exactly one line's worth of compression blocks?
> or schedule a deferred process and don't let the images be exported until that's done.
Good luck doing this on a battery-powered camera writing directly to an SD card that's expected to be mountable after removing it from the camera without an intransparent postprocessing step.