This is less of an issue with this specific instance (unintended/unknowable consequences for a powerful decision) and more with how D:OS2 (and the former game) handled shops and skill acquisition.
Skillbooks only being purchasable from a single unmarked individual per act is incredibly frustrating design, especially when it is so easy to upset or engage in combat with them without trying; but having these unmarked, unique vendors for each act be irreplaceable and potentially killing them being tied to some quests or common encounters is downright agonizing (Stingtail is the most immediate example of this once you start the game, followed by the Dwarf in the back of the Inn in Act 2).
Consequences that are reflected in the gameplay and story both are interesting and can lead to a deeper experience; but one wrong move or quest/Origins encounter done too early can completely lock you out of progression for your skillset for the better part of an act, barring RNG loot, and that's just heinous.
