How 'Remove Selected from Active Collection' feature works? I thought Shift+Alt+G (Remove Selected from Active Collection) was just a change to a collection.
I read the official manual and understood it.

But in fact, the way this function works in the blender is not only removing the selected objects from the collection to which the active object belong, but also the active object.
Please check the GIF.

What do I misunderstand?
The result I expected was as follows.


Additional Question
If so, how to check the active collection in Blender UI?
When checked with bpy.context.view_layer.active_layer_collection.name, the last clicked collection in the outliner is displayed.

This will also be displayed in the top left of the 3D viewport.
However, the active collection that the collection allocation operations mean seems to mean the collection to which the last selected active object belongs, not the last selected collection in the outliner.
I am curious how to check this active collection in UI.

Solution:
Ah, this was simple and basic.
To easily check the list of active collections to be used in the collection assignment operation, check the property editor\Object tab\Collections panel.
This is functioning properly, but you must understand two concepts:

The active object is one of the selected objects, always
If you remove an object from all the collections in a scene, it will appear as though they have been destroyed, although they are still present in the file memory. It can also still be loaded in another scene's collection.

The way I see it, Add Selected to Active Collection should be relabeled to Add Selected Objects to Active Object's Collection(s). In fact, if your active object is part of several collections, the UI will ask you to which one you want to add the selected objects, or if you want to add them to every one of these collections.
Similarly, Remove Selected from Active Collection should be relabeled to Remove Selected Objects from Active Object's Collection(s). It also prompts the user whith which collection they want to remove the selected objects from.
However, if by doing so you remove one or several objects from their last container collection in the scene, it will effectively disappear from said scene. You can see they are still in the file if you change the outliner display mode from view layer to Orphan data. You can then manually re-add it in your scene.
I agree that there should be a warning if you are removing an object from its last collection saying something like &quot;Warning : This will remove this object from the scene&quot;
To do what you want to achieve in your last set of screenshots, you just have to deselect the cone and call the operator.