Re: Should be (relatively) simple...
There is a substantial technical difference, and that difference is key.
Your Android or Apple device will continue working without second-by-second contact with the 'mothership'.
A Starlink device must connect to the constellation to function. The very first connection message with the satellite must include the terminal's accurate location, and that accurate location is essential to every subsequent packet exchanged.
The location is used by the satellite and the overall control system to decide which visible satellites will carry the traffic and how to communicate. The location is used by the satellite to (electrically) aim the antenna and to correct for the Doppler frequency shift. It's possible to lie slightly about your position and still receive the aimed signal, but the Doppler shift correction requires a precise location.
Yes, it would be technically possible to handle the Doppler correction and transmit shift spoofing entirely in your own custom designed ground terminal that mimics the identify of a legitimate one. But getting those ground terminals to work in the first place was a engineering achievement. No one is building an even more complex one in their basement.