I still see it as a tool change, in that it is swapping between two things that move with the workhead.
LinuxCNC supports tool offsets in all axes so it is easy to have this fixed offset in the tool table.
G54/55/56 etc should be used as workpiece offsets.
It will, of course, work either way (it's all just numbers) but touch-off will work better if this offset is in the tool table.
