The real restrictions on the use of mobile phones while flying has to do with the interference to the mobile phone network by transmissions from altitude. Some antennas are directional and would not receive the signal correctly. Signals can be received by two or more stations at once and that also confuses the system. In the worst case it can close down the entire cellphone network, although that is unlikely now. In the US it was made illegal to use a cellphone on an airplane only to protect the network.
It is incidental that some airplane systems are affected, although to an airplane driver it might be more important.