I've always read this as
"if you are claiming an inside overlap, you need to prove it at the protest"
"if you are claiming you broke the overlap, you need to prove it at the protest"
So one boat claims she has overlap, the other boat claims she broke overlap in the same incident. I don't see which boat the burden of proof is on?
If you ask for water, you prove you have the right for it.
If you deny the right to water, you prove you had the right to deny it.
One will have to come first (either the hail "no water" or "water")
So approaching the mark:
Inside boat calls for "water" (and it's a little tight) then you give it and protest them and they then need to prove they had the right to it.
OR
Outside boat calls "no water" (and it's a little tight) then you duck them and protest them for not giving it, they then need to prove that there was no overlap
