Compared to other HDMI-connected devices (e.g. Google Streamer fka ChromeCast, Amazon FireTV, Roku) or major TV platforms like Android TV or Samsung and LG, the market share that Apple TV commands is dwarfed. Apple TV devices are also very expensive.
A startup like Zwift that bets on Apple TV as a key GTM strategy is making an error in judgment. Apple TV is extreme long tail footprint.