Brian Williams says "hi".
The difference is that Brian Williams was deceiving millions of viewers after being repeatedly told by higher-ups "don't do that!" and hurting the company he worked for. Some comic who says "I looked up to Richard Pryor," and gets the fluffy fact wrong isn't. He may have misremembered and that's the end of it.
One of those is a Whew! blooper. The other isn't. Everyone has their own boolsh filter. It is up to each of us to use it, to download and install regular updates for it and to know how it works and how to interpret the results. We don't need a Truthiness Czar.
(In "Quizmaster," Mark Maxwell-Smith tells a story about when Milton Berle was on Hot Potato, and how he's being a pain in the neck. The question of "Who has been on the cover of TV Guide most?" comes up, Uncle Miltie names himself and is told to Sit Down. On YT there was (it might still be there) that particular episode, and so I went looking. As it happens Tom Dreesen gives the answer in question, not Milton. I don't think Mark was lying or being deceitful at all, I think he forgot what happened because it was nearly thirty years ago when Adam did the interview. It's just an honest and easy-to-make mistake.)