On satellite the mix channels are basically a HD channel that switches between multiple audio tracks as you use the arrows to "navigate" the boxes, and for certain things an interactive overlay that provides extra content like real time general election results, brackets for March Madness and Tennis/Golf tournatments, etc
Even if you get past the restrictions that some platforms have for developers when it comes to embedded HTML content or restrictions that require you to only use their internal media player, it's hard to replicate that experience on the app when they have to support 3rd party devices that have no dedicated channel, guide, menu, etc buttons on their bundled remotes, so the arrow keys need to be used for channel surfing and accessing the carousels and options while you are watching content.
They could just put the mix channels as is without the quick navigation option, but then you would have to dive into the options and switch the audio track anytime your preferred channel isn't the first one displayed, and deal with certain platforms that require you to use their internal player where the only way to switch audio tracks is to change your preferred audio language system wide. If they changed it so the arrows function as navigation whenever you tune to a mix channel, people with limited function remotes would get stuck on a mix channel everytime they channel surf between 204 HLN/205 SportsMix/206 ESPN or any other streaming channel that's adjacent to a Mix like your highest numbered local channel, MeTV, LIVE4K2, CNN, ShortsTV, FanDuelTV, etc
