Hi Protodd, you are right, If you are in wifi range, you won't be requiring Apple Tv to control devices which are homekit capability. If you are outside your wifi range, then you should be using Apple Tv to control those devices. Here i am speaking about app which can control all the devices, it is not restricted to lights or doors.(am not speaking about manufacturer apps.). For these kind of apps, Apple introduces to use Apple Tv as a hub, so that we can control accessories outside wifi range. But later in WWDC 2015, Apple announces HAP, where Apple Tv is replaced with HAP to control accessories.
I researched on this topic, and find out like they are no accessories which are manufactured to work with HAP. There might be some accessories which will be releasing in June 2016.
Thank you for your help.