Theta Z1: I can draw from the internal battery. Is this standard behavior or defect of my model?

I use my Z1 mounted on a robot and load its battery from the robot battery.
whilest working that out i discovered that i can draw from the Z1s battery. Is this normal? This is not possible with the other devices i use with inbuild batterys (speaker, beamer). Isn’t it standard that the battery should be protected with a diod? Is my modell faulty or is the Z1 constructed that way?
Just wondering and maybe warning, if somebody else thinks about trying to load the Z1 parallel with other devices, the other devices can empty the battery of the Z1!

I have not observed this behavior, but I also do not have the Z1 in parallel with other electronic devices. One behavior I have noticed is that the Z1 will turn on when and electric current is applied to the USB port. Is it possible that the Z1 is turning on from a power off state and then the battery is getting drained. You can observe the behavior with a cheap inline USB current meter, many of them have a log on the meter.

This playlist below covers several observations about the Z1 power states.