This device is FPGA, and not emulation. The chip recreates itself to act exactly as the N64’s chips would run. The benefits are that you get less input lag, more accurate gameplay, and you can use your original cartridges/controllers in a plug and play set up.
This doesn’t replace emulation, but if you are serious about playing older console games, Analogue’s FPGA products are a great premium solution.
Because, for a touch screen, the screen itself IS the user interface. Imagine while holding with one hand, you want to reach your thumb to the opposite corner to hit a button. Even if the body of the phone is the same, a larger screen will need a bigger reach for your thumb. That is primary issue.