Does a Split cutting edge have to protrude beyond the object to split?

Does a Split cutting edge have to protrude beyond the object to split?

e.g. I made a cube, then drew a polyline as the cutting object from corner to corner using snaps. However, the split failed. If I stretch the polyline beyond the cube it works. I expect I am doing something wrong, as this would mean using snaps on objects to draw split cutting lines does not work and a further step is required.

Does not work

Works

Hello - I see that and it also works to pick the exact-sized line up off of the top surface.The cause appears to be related to pulling the line to the target object - when the line sitting in the top face is pulled to the box as a whole, it gets pulled to the side faces as well:

image

When it is off that face it is pulled to the top and bottom faces:
image

@chuck - is that the expected result?

-Pascal

Not sure what happens here. This is @GregArden 's area.

Oops, sorry, guessed wrong…

-Pascal

Just repeated what you did? Lifted the line and it split. Is that how it’s supposed to work, or is that a bug? It means one more step for each split?