As an aside, it’s pretty noteworthy that even in a sample that voted anti-DPP in the same ratios as the actual electorate, you still get these results on the question of unification/independence:
It might just be more an American primary thing; when National Chengchi University took their 2024 post-election survey for Taiwan, their sample actually voted for the different candidates/parties in nearly the exact same proportions as the actual election.