I've never tried doing an 8-bit vs 10-bit-per-color "blind" test, but I think I'd be able to see it?

It's only really visible on subtle gradients on certain colours, especially sky blue, where 8 bits isn't sufficient and would result in visible "banding".

In older SDR footage this is hidden using film grain, which is essentially a type of spatial & temporal dithering.

HDR allows smooth gradients without needing film grain.