Just in case it's relevant to anyone - bear in mind that thanks to Larian's kooky engine design, it's entirely possible to Sneak Past many important game triggers, by literally sneaking through/over/past their trigger zones in game, in stealth.
You can? Maybe it is a case-by-case issue?
I was creeping in Stealth Mode past the gate of Druid Grove to avoid the battle there, but the cutscene with the Running Dog mercenaries and resulting Goblin attack still ensued ...