Maybe someone knows the answer to this. If source material is 8 bits per channel, and an 8-bit panel can faithfully show all the combinations, how would going to 10-bits for processing and panel make a difference? Where's the extra color resolution coming from if the source is only 8 bit?

If they are mismatched in any way or you need to do any kind of math, aka processing, then you want more bits. You do this because all of the math is generally done in integer format, so you do not have the ability to carry any type of remainder through a set of operations if your pipe is only 8-bits wide throughout the chain.

Bill