While it was limited to a handful of devices, Google added the ability to play HDR content to its Android app a couple of months back. And even if these devices were more on the powerful side of the spectrum, some have noticed performance issues once videos pushed to 1440p or above—the clips stuttered with dropped frames. To remedy the situation, YouTube has opted to take out these options. Now, HDR maxes out at 1080p so you can enjoy the content without the problems.
Source: Android Police