Here’s what Niantic say about Wayfinder rating
Your Wayfinder rating will improve as the number of decisions you agree with grows, and your performance rating may be lowered if you have too many Disagreements. Your rating may also decrease if abuse of the Wayfarer platform is detected. If your performance is poor, please take the time to re-evaluate how you are analyzing nominations based on our acceptance criteria.
So they can decrease your rating if you abuse the system. Your rating is also taken into consideration.
What’s funny is that in my last 7 nominations the upgraded nomination took longer to review. I had 2 nomination rejected after 4 days and upgraded nomination accepted after 6 days. Before that my upgraded nomination got accepted after 3 days.