I just tried, and while it does decode a 6kx3k 60 fps video, which is very admirable, it doesn't hold 60 fps while doing it. There are probably encoding options to minimize work on the decoder that could let you push it a bit more. MediaExtractor seems to be arbitrarily limited to a lower resolution, but that can be bypassed.

Can you try with skybox vr? At least on my note 8 Oculus video really doesn't like h265 video that's more than 4k.