No brink to any of their impacts. The fracturing in evidence standards started with the creation of the PTAB during the AIA thirteen years ago.
Paul Morinville 9-13-2016, founder and former President of US Inventor, Inc., executive at multiple technology startups including computer hardware, enterprise middleware and video compression software in the U.S. and China, and now medical devices. IPWatchDog, “How the Patent Trial and Appeal Board Harms Inventors,” https://ipwatchdog.com/2016/09/13/how-the-patent-trial-and-appeal-board-harms-inventors/id=72554/, //ff
Prior to the AIA, a challenger to a patent had to prove with clear and convincing evidence that the patent is invalid. The challenger had to be related to the patent in some way and generally that meant they needed to be sued for patent infringement. It was the challenger’s burden to prove the patent invalid. The challenger bore a significant cost – often as much or more than the inventor bore.