I realise this looks a lot like the other topic: Workouts adding too many calories to Apple Watch
However I wasn’t sure whether you consider this the same problem. Feel free to merge the topics.
The problem is very simple: I did an 11 minute foam roller session and right after that a 20 minute flexibility session. Freeletics logged no less than 160kcal for the foam roller and 302kcal for the flexibility session. It also logged the sessions as “functional strength training”
I suspect this is a bug.
To be clear, there is no double registration of any other devices, the data written to Apple Health by Freeletics is 160kcal and 302kcal