From my LIMITED understanding, button mapping only plays a role in Revit when you are using Design to Fabrication to convert family content into Fabrication parts.

Route and fill works a little differently.....As i understand it, the parts available for route and fill are determined by joint connectivity. So it looks at the connectors on the ends of the parts and attempts to think through possible solutions within those constraints.....You will need to investigate which connectors the drop cheek wants to have and look at the connectivity in the connectors database to find out why this isn't working.