It can be a silly question but this statement seems confusing to me
The ADT-1 Developer Kit is a streaming media player and game controller designed for running and testing apps built for Android TV. Supplies of ADT-1 are limited and it is intended for developers who are interested in building new apps or extending their existing apps to run on the Android TV platform.
Note: The ADT-1 kit is not required for building and testing apps for Android TV. You can build apps for TV and test them using an emulator for TV devices. The Android SDK includes all the software needed to build TV apps and an emulator for running and testing them. For more information, see the Get Started guide for TV apps.
There is no single word about developing on real devices, only ADT-1 and emulator.
Can I develop Android TV app on real device such as NVIDIA Shield TV, Razer Forge TV or just "real" TV like Sony Bravia without ADT-1 kit?
This guide, from the Sony developers website, shows the steps to connect a Bravia TV to the ADB shell through a router. The TV must be configured as a developer device (the same way you activate Developer Mode on a phone).
You can also set consoles like the NVIDIA Shield and the Nexus Player in developer mode and connect to them using an USB cable, just like a phone, but use the right cable, as the cable that comes with the Nexus Player is just a power cable and it doesn't transfer data.
So yes, you don't need ADT-1.