Steps to reproduce

1. Add a scoreboard to record the “Distance by Horse” statistic

   /scoreboard objectives add test custom:horse_one_cm

   /scoreboard objectives setdisplay sidebar test

2. Sit on a saddled camel and rotate the camel with the mouse

   /summon camel ~ ~ ~ {SaddleItem:{id:saddle,Count:1}}

   → The score increases

Note

Riding a camel increasing the Horse statistic rather than a new Camel statistic  is another report