I think the change in US Patent law is to bring it into line with the rest
of the world. Previously a US, note US only, company could produce lab
notes or similar to give an earlier priority date than the filling date.
The change isn't saying you can't use prior art outside of patents to
invalidate a patent, it is just saying you can't back date your priority
date. At least that is what my works in-house lawyer said the change was.