Interesting, I feel this lives somewhere in the intersection of bug and feature. Happy to leave it in but.
Generally if a site setting says post it should relate to the op and replies if a site setting says reply then it is just to the responses.
So in this case I think it makes sense to expand scope.
Keep in mind we are moving all these kind of site settings to be group based, so we probably will be able to take care of it with the same change.