In Cura I have previously moved a model somewhat below the build plane in order to quickly test something on the top part as seen in the picture.
The “view GCode” seems to suggest that PathIO only slices the top part. However, the time estimate is for the full part.
In fact looking at the Gcode the first layer reads
; PATHIO: New layer ; layer 1, Z = -17.799999 ; PATHIO: Starting new track ; tool H0.200000 W0.400000 ; skirt ; indexLimit: 21 G92 E0.00 ; Set the current filament position to E=0.00 G1 E-3.00 F2100 ; Retraction G1 X139.40 Y140.00 Z-17.80 F5100 ; Travel
My guess it that the attempt to move to Z=-17.8mm would cause a nozzle crash. Especially for people (like me) with a BLTouch.