Assuming that's true - there's evidence the other way, of course - the question is why devices are permitted on board at all. If there's even a possibility that an active device can interfere with navigation and/or operation, the policy should presumably that they not be permitted on planes at all.
Because apart from those actively disobeying as in the OP, there are countless more who forget to turn their devices off.
Please, read at least the executive summary