Moving the second wire up towards the first sharpens the overall pitch of the reed. It does on my shapes anyway (Fox 1 or Herzberg).
I have seen such a variety of wire positions and lengths of reed that I have long since departed from any set position as gospel. But slipping the first wire back towards the second also changes things and makes a slightly less resistant reed which is easier at the bottom but then not so supported at the top.
There are many other factors of course (variables) like the tightness of these wires and the scrape of the actual blade.
I was finding I needed to make a reed 25mm from shoulder to tip to be up to pitch on a Number 2 crook and couldn't work out how an ultra long reed like a Danzi would play at pitch. One of the factors is the wire position.
This is not the end of the search but just a bit of info that I couldn't find on any sites after a bit of googling so decided it warranted a blog post.