That's off by a decade.
> 256 color monitors
Is that a thing that exists?
> We've only switched to 10 bit because of HDR.
You can get clear banding on an 8 bit output, and 10 bit displays are used at the high end. 10-bit HDR isn't immune to banding, since most of the increased coding space goes into expanding the range. There's a good reason for 12 bit HDR to exist.