Ah... no. It must have been patch 6 (the romance patch). Looking at my screenshots folder, I defeated Ketheric on 19th January 2024, so that would have been on patch 5. I started replaying act 2 by 25th March 2024, so that's patch 6. I remember there had been a major patch when I looked into the different behaviour, and checking to see if GOG would let me downgrade but I think the old files had gone by then. It could have been changed in a hotfix, but I think it's more likely someone forgot to add it to the changelog.
