I can't help but wonder if this was due to tight deadlines or budget constraints.
Apparently not - see Community Update #24, it has a paragraph which explains their reasoning.
In fact, after CU 19, I personally have a lot of doubts about the answer in CU 24. The inconsistencies and gaps in the game are too noticeable. It's just that if people change the concept it happens more smoothly. But, in any case, we won’t know, now I just want and hope that they will refine and expand what is in the game (Although I will remember the situation with the upper city for a long time) For starters, I would really like to see the normal ending of Astarion x)