I think it’s a byproduct of the show choosing to adapt events from way further on like the concluding the Reanimen, Flaxans’ returns, Sequids, & Machine Head, so early that makes the reunion with Nolan happen so early. It’s technically still right time its just a lot of Mark’s adventures after he left happened when Nolan was around.

As for stuff we missed It’s really just the teacher bomb vest, Sanford, Capes interlude, and some quality of life stuff.