Both BOX (0x0042) and CIRC1 (0x0043) can be of the PLC (Closed polyline) type.
BOX only requires 4 vertices, it was geometrically AND logically closed, removed a duplicate.
CIRC1 was geometrically closed, it only requires 2 vertices when logically closed.
TRACK1 (0x0054) is simplified as a line segment.
As open polyline it only requires 2 vertices, removed a duplicate, QCAD stored it as an L (line) type, its simplest form.
It's a bit counter-productive that the Linetype rendering engine must handle duplicate vertices for each shape to include.
Regards,
CVH