It means that we do not support single channel packet forwarders on The Things Network and on the forum and that we condemn their use. Be aware that not supported also means that they are not guaranteed to stay working in the future whatsoever.
As you were also talking about an outdoor ‘gateway’ you really should consider to go for LoRaWAN compliant gateways. That will just work as designed, without having to perform non-LoRaWAN compliant hacks that negatively impact operation of the network and other users and will be much easier to get support for.