No problem, I‘ve reverted this change because it would have been very hard to fix the geometry.

If you want to re-add the relation for Ease Gill then go ahead (I’m afraid I couldn’t keep that when doing the revert). imo it’s a good idea to keep boundary lines separate from stream centrelines and other physical features. It’s too difficult to satisfy the requirements for the geometry for the boundary and for the stream with one line. :)