That is absolutely not true. Horizon sells both the Spektrum DSMX receivers and the JR DMSS receivers.

That being said, the Spektrum DSMX RF link is way behind the times. All of the radio manufacturers in the market (even the HK off-brand ones) use an RF link that is more robust than DSMX. That, and given the problems that some have had with Spektrum hardware and software (above are a few examples) I'd go with JR DMSS over Spektrum DSMX 8 days a week...

Bob