The shell is not very thick. The threads never really have a chance there to close off fully the opening on their own, without a washer. Some water, of course, will remain, but that this granted under any circumstances. One just needs to come to a situation where the remaining water has a chance to evaporate over openings that it might have come in.

With the Mike's trick, I am afraid of the opening working too much both ways. Of course, this spoke would need to be bent outside or flattened as well and one could do it with a loose bolt as well, say with a locknut.