I don't get your point. This article is about control of the high level software running on your phone, not the firmware controlling your phone's radios. Even if an app store allowed any software without filter, this would not allow anyone to transmit "arbitrary radio signals". The much lower level firmware ensures that the radio communicates at proper power and protocol.
The phone hardware is not capable of arbitrary radio signals anyway. People can buy software defined radios off the shelf, but people generally don't abuse this because a) there really isn't any motivation for them to and b) they would quickly land in really hot water with the FCC.
The phone hardware is not capable of arbitrary radio signals anyway. People can buy software defined radios off the shelf, but people generally don't abuse this because a) there really isn't any motivation for them to and b) they would quickly land in really hot water with the FCC.