@DanK thanks for reaching out!
Prop 65 requires products sold in the state of California containing one or more of a list of 1000+ chemicals of concern to the state of California to notify customers of potential hazards. Because different companies adopt different approaches to manage compliance with this labeling expectation, we would second the state program’s advice to contact the manufacturer directly if you would like specific information on why a label is used on a certain product. You can reach out to Elite Bike Trainers with the contact information at the bottom of their webpage, here.
I hope this helps guide you in the right direction. Thanks!