There are no known hardware decoders for 10-bit H264 in the world. It was a format that was pretty much only used by a few anime groups, so no one bothered.
Parts of 8-bit x265 can be offloaded to the GPU on Pi.
Vero 4K can play back 8-bit and 10-bit H265, but 10-bit H264 is not possible. There is very little demand for playing back this format.