the party reacts/moves correctly, but although mobs could potentially see a stealthing party from an upper floor balcony, I was surprised when detonating a casket on the upper floor I also triggered one below it
thanks for the tip, I'll check it the next time I'm in-game, bc I honestly can't remember now. either way it is a bug, just its nature may be different
EDIT: you were right, I haven't picked any spell for this tier. so it seems the problem is with the game showing the empty slot at all
in Eder's abilities tree under Fighter Stances only Defence Stance has an explanatory pop up attached to it
in Xoti's skills panel the Total Stealth shows 2 although the composite part states PC 2, Eder 1