Apple Watch question

I have the same issue when switching from a Fitbit to AW. I've read a lot about it. The Fitbit and other trackers calculate calories burned from exercise/activity AND what you burn just being alive. The AW only gives calorie credit from exercise/activity. So, on my Fitbit, a 45-minute walk would give me 300 calories but the AW only gives me 200 because I would have burned 100 calories just being alive during that time. It also only gives calories for effort, not steps. If you walk 10,000 steps a day but don't get your heart rate elevated, AW isn't going to give you calories for that.