Does Dolby Atmos on HomePod work with Apple TV HD?

Does Dolby Atmos on HomePod work with Apple TV HD? I know Apple TV 4K says Dolby Atmos works on HomePod, but I was surprised that my Apple TV HD can easily connect and use my HomePods as speakers. But I'm not 100% sure if I'm getting Dolby Atmos sound out of my HomePods or not. I guess I'm trying to figure out if you get Dolby Atmos sound from the speakers themselves, or is there a software requirement to turn the sound into Dolby Atmos that's needed from the Apple TV 4K that my Apple TV HD doesn't have. Anyone know?