Hearsay would be if someone else said a Google engineer told them that Google was biased. If a firsthand accusation from an engineer is hearsay then whistle-blowing of any type wouldn't be a thing.
Yes, what he said is hearsay because it's a bunch of work rumors from an unreliable source. I have no idea why I should trust Cernekee (let alone why any US President should trust him enough to make this type of public accusation), it seems like he has some "unfortunate baggage" (https://www.cnbc.com/2019/08/06/google-whistleblower-cerneke...)