I believe 11.0.3 / 11.1 / 11.1.1 / 11.1.2 are currently signed. It might be that with the recent iPhone x release there are more versions available. Or since there are no exploits available there is no reason to disable signing and force everyone to use the latest. It is as much a mystery as to why 32 bit apps slow down iOS devices, especially since they were designed for older hardware.