Astarion in any case say "I'm so much more than what you made me!". Basically, this means as a character, he always changes after his quest.
When you say Ascended Astarion has changed, you are missing that Spawn Astarion is also changed. I really like what his writer, Stephen Rooney, says in an interview. How he created two versions, one becomes gooder and the other more evil. Both versions differ from how you knew Astarion before this situation.
The only plot gap for me is the moment if you kill Cazzador without Astarion, and Astarion changes anyway. He yells at you, but you'll still get a spawn romance scene, even if he hasn't passed his redemption.
The player's character may notice this and react with phrases.
but for ascended literally "you're not soft enough"
I'm surprised you can't interrupt graveyard scene and just walk away, but you can leave bite scene in two ways. For some reason, you can also change your mind about breakup with Ascended Astarion three times. At almost every phase you will have "Sorry I changed my mind!", but there is no way back with Spawn, as soon as you click "I want to break up" you can't say "I changed my mind".
++++Still in shock you need 20! 20!!!! to change his mind. and 15 after
even if you have a good relationship
standard phrase before the ritual also implies Astarion becomes "better" in two different concepts for him. better as stronger, or better as kinder ^-^
People who like evil Astarion immediately notice changes in his good version. People who like soft Astarion immediately notice changes in his evil version.
My point is: there are always changes, it will never be exactly the same. Both versions show what was already in him, but brighter.
^-^ I like that