QLayoutItem does not delete anything, same as all QLayouts.
QLayoutItem is not a layout, rather, it is a layout item, so I don't understand your comment.
On the contrary, layouts are also layout items (it is so in order to allow sublayouts).
@onek24 You're absolutely right. I didn't yet grasp that the QLayoutItem in fact behaves as a kind of proxy for the actual widget (or child-layout). Thanks for the clarification.