I know it may seem strange, but picking it up doesn’t have anything to do with motion detection for this device. It’s a PIR sensor for that. So “motion“ is actually a change in temperature passing across the field of the sensor. Once you pick it up, the heat of your hand is going to be essentially equal no matter what you do next. So no change, no report from the sensor.
The following FAQ explains The detection field for this kind of sensor:
FAQ: Where to locate motion sensor for fastest response?
As far as the variable Behaviour you’re seeing…What are the reporting interval settings?
Parameters 2, 3, and 4.
The “always active“ parameter just means it will report during both daytime and night time. It doesn’t change the blind interval.