Imo size is really just an emotional play. It's less "gross".
The real question is ethical about the fetus development, pain, nervous system, etc.
Then there's the ethical and technical aspects of access for a woman.
Hard to hold her accountable if you make her save money and travel for states away to terminate when her decision was made 8 weeks earlier.
We regularly wait until 18-22 weeks to find many major abnormalities that might cuz a woman to decide to abort. That information wasn't available earlier. Judging just on time is arbitrary and ignorant unless only discussing elective termination for nonfetal related reasons.