People have been having issues with expressions since early access. There's a popular mod to fix the worst contenders, reducing wrinkling to varying degrees. If you want to play a stoic character as of now, it's impossible without mods for many popular races/species. People have shut up because we have mods now. It's me. I am people. I am part of the crew to have b*tched about this for ages.
I haven't seen a single post in here asking for Tav to look terrified of Astarion when kissing him until patch 6 happened.
That would be because looking visibly and unexpectedly terrified is the opposite of being stoic. Nonetheless, people have had criticism for how much or little emotion the game conveys for a long time. This scene is the latest incident, and seemingly the most controversial. What the mod does is bump people up to 3 varying sets of intensity (normal, reduced, severely reduced). Be aware, this will be applied to all scenes Tav is in. It was NOT created for Astarion romance.
Funny, I could have sworn the criticism of this scene was that Tav previously looked visibly happy and completely not terrified, like here in patch 3, for example (just before and after kissing Astarion):