The Advanced options
"Make window managers treat the panel as dock" and
"Reserve space, and not covered by maximized windows"
are legacy options left over from the predecessor of LXPanel.
(Technically, the first causes _NET_WM_WINDOW_TYPE_DOCK to be set as _NET_WM_WINDOW_TYPE, and the second causes _NET_WM_STRUT[_PARTIAL] to be set on the panel's toplevel window.)
I would like to consider removing them in a future release; that is, the ability to disable these actions. If anyone runs with these options turned off, I would like to hear why.