I got the new fitbit air, it came with 3 months of “AI coach”. To give it a try, I asked it how it detected my stationary bike ride, with only a sensor on my wrist.

It gave me a confident answer about vibrations, pulse, etc. I checked the linked source - it was a years old reddit conversastion about another fitbit watch, where comments were guessing about the automatic detection of workout types.

I turned off the AI feature.