Larian is not going to script, record and animate entire cutscenes just in the hopes of misleading future dataminers.
BUT.... BUT.... I did read an article that talked about the romance scene and apparently there is a juicy line about you suddenly thirsting... or hunger... or some such reference that hints that you might be turning.
There is no such line in the romance scene. There's a line like that much later on, but it has no connection to whether you let Astarion snack on you or not. And being turned doesn't work that way in any case.
