Youtube only supports surround sound on movies on the platform, that are technically from Google, and only for theatrical movies that are free or to be purchased. Normal content creators do not have the ability to upload in surround sound and if they do its converted down to 2.0 stereo. If you want actual atmos content you have to download it directly from dolbys site or play a movie via the Apple TV app on the Macbook Pro that supports it. Atmos content at min is coded in 5.1.2, the .2 is for the atmos channels. if that info isnt being sent to the laptop your not getting it. Additionally the atmos effect on a macbook is nowhere near what atmos support should really be like, its just nice that apple supports it for content creators who have it connected to a AV receiver that supports it when creating theatrical content, where this previously did not work without an external card.You've got a source for that? Dolby lists YouTube as a platform that supports Atmos.
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These videos are demonstrating object-based Dolby Atmos which I always had in my mind that it could be done as long as the virtual speaker sounds almost exactly matched what our ears normally hear from true Dolby Atmos. So whatever these videos are using to stream the sound codec is definitely working as my ears beg to differ with your theory.
