Yes, I had read that Meltzer had shot that down last night, said there had been no talks between AEW and Lesnar. And we know Meltzer is well-connected in AEW.
I'm pretty sure the rumors emanated from WWE, where they are seeing things on their end in communications (or lack thereof) with Bryan and Punk leading them to conclude they are signing/signed to AEW.
They should have realized it's just impossible to keep secrets that big under wraps for any length of time. Black was an anomaly that was played to perfection, but if they were trying to surprise the audience with their debut, they would need to debut them immediately after signing.