The picture that is shown under the Printer Origin heading is not the print bed as stated. It is a picture of the print head and the nozzle position relative to the edge of the print head.
This is so you can set the print head to the end stop and have the nozzle on the edge of the bed. This normally only needs adjusting with a Z probe but can be used to ...
I had the same problem, solved it by inserting
// Move X and Y to 0 after homing
process_subcommands_now_P("G1 X0 Y0 F5000");
at the end of G28.cpp, just before ui.refresh();
This moves the print head to X0, Y0 and leaves Z untouched after the homing procedure. This way any oozing that might happen while the extruder heats up will be outside of ...