Okay, I found it. It’s been so long since a mythic lined up
I’m already chasing up how the in-game news works, because I think it is a default line of text, so it doesn’t vary based on if a Mythic is releasing before it’s Kingdom week. As in, it doesn’t auto update to include it’s exclusive in all chests, including Event chests when mythic and kingdom weeks align
I’ve also updated the blog in the meantime, and also let our Prod team know to look out for future instances where this happens.
edit: I also just checked the game guide on Mythic troops and it looks like it wasn’t missing from there - it does mention Mythics will be exclusive to all chests during a Mythic’s kingdom week