It does warn you that if you go on into the mountain pass, the game will advance, and that you should tie up any loose ends first.
Oh sure. I've played through more than once. It just surprised me that this time there was a consequence.
As far as I'm aware, if you haven't reported Minthara's death to Halsin when you leave the initial area, the tieflings that are still in the grove at that point will disappear and never return.
Ouch. I really hope I haven't lost them all on this playthrough. I'm playing a sorcerer, and I was looking forward to Alfira's robes.