Apple Watch and Suunto Smart Sensor

Hi,

I was using Suunto Ambit 2 and 3 watches for 2 years to track my gym activities, but last month I decided to give the Apple Watch a try. After 2 weeks I've added the Suunto Smart Sensor to the game. No problems pairing it with my Apple Watch and getting pretty accurate readings, but apparently the Workout app seems to not use them at all. In fact, the results using only the AW sensors are higher than the ones stored when I was wearing the chest strap. Does anyone know why it happens and how to make the watch use my Suunto Smart Sensor readings?