Sulin appearing with Rand’s group was NOT an error. Perrin is approximately a month behind everyone else in the timeline and will play major catchup in Towers of Midnight .
Brandon clarified later; this was an error.
If you are viewing this on github.io, you can see that this site is open source. Please do not try to improve this page. It is auto-generated by a python script. If you have suggestions for improvements, please start a discussion on the github repo or the Discord.