This all traces back to the Keith Smith CelticsBlog post, take anything he says with a grain of salt.
Why do you think he's not credible?
I’m not the one who lobbed the original criticism, but he was the initiator of the Blake Griffin rumors a couple of summers ago, based solely on his hearing Ainge was going to San Diego after summer league. It wasn’t like Ainge had children and grandchildren in San Diego and LA, and after summer league is typically the only time NBA GM’s get something resembling a vacation for a couple of weeks.
I don’t think he’s completely lacking credibility, but I agree that what he says needs to be taken with several grains of salt.
He's a Real GM/Celticsblog writer who got himself a blue check mark on Twitter (it's easy to do now). I don't think he completely fabricated the whole article, but I think a lot of it is probably what he "heard" while hanging out at summer league, plus his own observations. His credibility comes from his cap sheet knowledge, which he is very good at. But he's just some normal working schmuck like the rest of us who pretends to be an insider by night. It says right in his Twitter profile "Still seeking FT employment in basketball!" Would you trust a mailman who's looking for full-time work as a dentist to fix your teeth?
He does retweet and give credit sometimes, but he also follows up on Woj/Shams/Stein/etc with "confirmations" that their tweets are true, as if we needed him to confirm that info. He grabs a lot of info and sends it out as his own, like players singing overseas or contract figures. I highly doubt he's as plugged in as he tries to seem. It's a show. So again, take anything he writes -- with the exception of his cap sheets -- with a grain of salt.