Pardon my ignorance - but I have never heard this before (or seen it in any documentation). Where does it say that DVI is only an 8 bit pipeline?
Found this on the net in response to your question:
It's all very well saying a panel is capable of 10-bit colour depth (1.07 billion colour palette) as opposed to an 8-bit colour depth
(16.7 million colours), but you need to take into account whether this is practically useable and whether you're ever going to truly use that colour depth. Apart from the requirements of your application, operating system, graphics card and software, one more pertinent limitation is from a display point of view, where there must be an interface which can support 10-bit colour depth. Thankfully the PA271W-SV does include a DisplayPort interface capable of handling a 10-bit colour depth. If you use the DVI interface
you can only take advantage of 16.7 million colours.
This is from TFT Central and is part of a review of the PA271W-SV.
I confess that I had no prior awareness of this either.