I do hate that certain cutscenes trigger on whoever the closest party member is and not the controlled character (usually the MC for people), but I'm pretty sure there's a setting in the options that can auto select your MC after finishing a fight/exiting turn-based mode, have you tried checking that to see what your settings are and if that would help? If its not a settings issue for you then I agree with you on having Larian force the MC to get the convo as the default.
I've only had this issue with non-combat related cutscenes (Like meeting the 2 brothers arguing with the hag on the road and Shadowheart triggering the cutscene because she walked too close to them while I was collecting plants).
