Bug Elements lose :active pseudo state when not hovered

I have a scrollbar in the runtime which I wanted to style to give feedback when it is grabbed by the mouse. Selecting it with :active to change the color works great at first. However, if you hold the mouse button but drag outside the scrollbar area, it will loose the :active pseudo-state even though the interaction is still ongoing. If you re-enter it while still dragging, it will regain it again. This is a very confusing interaction.

Since this is not consistent with css I am considering it is a bug