Eastport Pram mast hole

i think I saw something about this earlier but can't find it again. On the Eastport pram bow thwart, there is a square cut-out for the mast and next to it there is as small hole drilled in the thwart. What's that for? It's not on the blueprint or the instruction booklet.

 

I think that hole was for an optional way to run some rigging.  I didn't bother with it, just cleats installed on the wooden mast.