It seems to me that this stems from a misunderstanding about what a UIPanel actually is. It could be that the naming is misleading and should be called something akin to "DrawCallCollection".
A UIPanel is not a "panel" like a window or view, it's only the responsible for drawing the widgets inside its sub hierarchy, not for defining screen areas or anything like that, like a UIView would be in native ios development.
So your Shop Panel is not a UIPanel, it has a UIPanel. The two words panel just mean something different.