One of the 200k brevets that I did in 2019, one gal did it on a fat bike. I almost caught up with her after about 120k, but she got up that hill too fast, I did not see her again until I finished. At the finish when i saw her, she said that she had a lot of trouble with her bike. She had new shifters installed and the right (rear) would slip into high gear, bar end shifters. After a while she got tired of manually holding the gear shift lever and just pedaled in high gear. I looked at her shifter, looked like the bike shop did not tighten a screw tight enough, but I never worked on Microshift bar end shifters so I might not have diagnosed that right.

I am not a high wattage rider, but it is embarrassing if someone beats you on a fat bike. More so when their shifter causes them to pedal much of the distance in a bad gear. Later Kingston said she did a 400k or 600k (I do not recall which Kingston said) on that fat bike too.

So, you never know.