The intensity percentage displayed during your workout is a preliminary calculation. This value is recalculated and refined once the complete workout data is processed and stored in your workout history. This recalculation may result in a slightly different percentage being displayed in your history. Therefore, the 100% you see initially is not the final value.
If you exit the BODY BIKE app, for example, to change music or reply to a message while cycling, the app will lose connection to the bike. During this time, power and cadence data are not received from the bike, which is used to calculate speed and distance, although time continues to be recorded. This loss of data can be a reason why the intensity may not show 100% at the end of the workout.