That started when GM trademarked (or renewed?) the name "Zora". They just renewed it again. I'm happy to be proven wrong but I've not seen anything released from anyone that actually works at GM that confirms there is going to be a ZR1, Zora, E-Ray, GS, or anything other than the Z06. I believe there were recent public statements confirming an electrified C8 but even that is recent and not at the time they unveiled the C8 which was the point of this thread.
As for gmauthority, they are wrong as much as they are right and the article posted above is based on a leak from someone who supposedly works for GM and is not a formal acknowledgement from GM.
All that said, everyone who follows Corvettes assumed from the beginning there would be a Z06, ZR1, and GS variant just like with the C6 and C7. It just hasn't been something GM has every confirmed until they are ready to unveil the car. Cadillac doesn't have the history to go on.