Wrong panels preferences displayed and edited in the administration of a page when it's not a top level page

How to reproduce:

• in the wiki administration, in the Panels section, choose to display only the left column of panels
• create a second level non terminal page as follows:
  • create a non-terminal page
  • create another non-terminal page as a child of the first page
• go to the Page Administration of this page
• go to the Panels section
• choose both columns layout
• set some panels on the right column
• save
• exit this page administration
• enter again this page administration, go to the panels section

Expected result:

• the columns layout displayed in the panels administration is the 2 columns layout, with the right panels set as set in the steps before
• it's possible, at this point, to modify the list of panels displayed on the left and on the right, if needed, from the inputs

Actual result:

• only the left columns panels is displayed in this administration section, as set at the wiki level
• the rights panels input is displayed but disabled and it's not possible to modify it
• the right panels are not displayed at all, so even using the panel wizard it's not possible to update the list of panels displayed on the right.