Thread:SonictheHedgehog1245/@comment-26897822-20171006193239/@comment-24908786-20171010233238

Well, I read over the episode transcripts, which have been posted on the MLP Wiki, and after Celestia and Luna entrust the Mane Six, Starlight, and Sunburst with looking into what happened to Star Swirl and the other Legends, they have no idea of the adventure that occurs with the Pony of Shadows until later on, when the Mane Six, Sunburst, and Starlight bring Star Swirl and the other Legends to meet with the Royal Sisters so Star Swirl can see how they've changed since he last saw them.

I also read that Celestia and Luna allow for Star Swirl and the other Legends to depart to see how much Equestria has changed since they last saw it, but assure them that they are always welcome in Canterlot. They also joke about how they might still need to turn in some essays Star Swirl assigned them to work on before his disappearance.