Contains spoilers for TWatWK and PoYD (sort of)
So I haven't actually read PoYD...so I'm slightly unqualified to suggest this theory, but from other readers I've heard that Oskar is REALLY excited in PoYD to tell the people there about what happened in Anniera because they apparently haven't heard it yet.
Now will someone please give me a good reason as to why Oskar would be so happy to impart news if Janner wasn't alive? There's NO WAY he would be that happy if Janner was still dead! He's known Janner for so long and, personally, if my favorite student was dead, I wouldn't be so excited, even if all the amazing things that happened in Anniera had happened. Therefore, I think Peterson is alluding to the idea that Janner comes back to life after the visit to the First Well through this instance.
And now I'm just waiting for the onslaught of people who will swoop in and disagree with me and tell me I have the context of the situation in PoYD wrong 😂😶
Janner's death marked the beginning of the Fifth Epoch, so it was the year 5/1 when he died, and TPoYD is set in the year 5/3 so it has been quite some time since Janner died.