So Onmund and J'zargo just walk straight past Tolfdir in my current playthrough and Tolfdir only tells Brelyna what to do. It's not important for the gameplay obviously but it is nipping me to no ends.

What does he tell the other two apprentices to do?

I can't remember. I've tried reloading and re-entering, etc. It doesn't help. Maybe it has to do with the fact I left the mission for a few months; I was severely disappointed when I with my other character. It made no sense to me so I've purposely taken longer to get round to it this time.

Tolfdir probably just had them run off and buy ice cream for everyone else. That's why he didn't follow you through the first half of the dungeon, he was still trying to finish his cone.

There's ice cream somewhere in Saarthal? Must be the real reason he 'adores the location'. The truth is out.