it doesn't matter what time you start the section, only that you a) finish all the questions, and b) answer as many correctly as you can. if you start the section late, and can't finish the last few (and leave them unanswered), you will be heavily penalized.
i would also assume that if you rush through the section (because you started late), that you would be more prone to making silly mistakes that you wouldn't have otherwise made. so in this case, i think that starting late would affect your score.
my GMAT debrief:
https://www.beatthegmat.com/came-through ... 44327.html
You will not fear the terror of night, nor the arrow that flies by day,
nor the pestilence that stalks in the darkness, nor the plague that destroys at midday.
A thousand may fall at your side, ten thousand at your right, but it will not come near you.
- Psalm 91: 5-7
