Thank you @sven, You right, this is bad idea to draw conclusions using this function.
I was wrong, and in both situation this atlas still in memory.
But question still open, how to a counter works (it depend of (linked to) collection, GO, factory or something else?).
I tried to make collection factory and exploit this bug, but texture still in memory after removing spawned GO. That one of the reason why I want to know how it works. (it is easier to use something when you know how it works)