I personally found the “Awake Detection” feature to be quite accurate until you changed the algorithm with the 20181212 update. It now (20181212) assumes (incorrectly) I am awake if my heart rate is high (110 for ex.) but movement is low (as in deep sleep). I would think it much more likely that I am dreaming in this situation. This occurred multiple time per night.
I use a Mi Band 3
I would post and example chart but I have now uninstalled 20181212 and am using 20181011 instead which seems to get its awake detection right.
If you improve the awake detection as outlined above could you please post details in the updates release notes so I will know when it is safe to update.