Maybe we should be clear about which beliefs we're talking about.

If your claim is that he doesn't believe Greta Thunberg specifically is the Antichrist, then sure. But that's just listening to the words that he says. He never says he believes Greta is actually the Antichrist.

"In our world, [the Antichrist] is far more likely to be Greta Thunberg [than Edward Teller or other mad technologist, or implicitly weapons and surveillance tech manufacturer Peter Thiel himsef]."

He does actually believe this.

So yes OP is correct that Thiel said and does actually believe Greta "is potentially" the Antichrist. But that's a different claim than saying that she actually is the Antichrist. There are thousands or millions of people (most unknown to Thiel) who could fit into the Greta-Antichrist category broadly. So it's a much weaker claim than that Greta is herself singularly the Antichrist.

Both claims are equal levels of insane though. If you believe the weaker claim that the Antichrist would be someone like Greta, it requires exactly zero additional insanity to believe the stronger claim that Greta is actually the Antichrist.

Exactly. The literal claim is just a fig leaf for being able to say 'oh, he surely doesn't mean that' whereas the subtext is far more important and he definitely believes that based on this and many other statements and actions in the past.