Thank you for providing the link and narrowing it down to a specific time.
I have watch it, spent 30 minutes of my time that I'm never gonna get back

. There is NOTHING relevant to our conversation in that stream. They have said nothing except that your actions/attitudes/feeling towards your companions will influence their development. Well, that was obvious to begin with. There isn't a word about Astarion's personality/story besides them telling us that you can become a vampire depending on your choices. Nothing on the lore of being ascendant, nothing really relevant to our discussion here besides general info that your actions count.
This is a reply to Rhea, to a post with a link to a game stream