I know that you already have the answer, but here is my spin on playing with the adjustment rod.
Last year I bought second hand 2010 Nordica GS skis with the same XBi CT bindings. The Nordica rep told me later that I should not be playing with the forward pressure adjustment rod as it is calibrated in the factory.
Since the binding plate adjusts in increments of 5 mm. of boot sole length, then if my plates are set to 305 mm., then I conclude that the bindings should tolerate boot sole lengths of 305 mm., plus or minus 2.5 mm. My reasoning is that if Nordica is going to put the exact number 305 on its scale, then I imagine that they are talking about boots ranging in size between 302.5 and 307.5 and not about boots between 300 and 305 or between 305 and 310, but I could be wrong.
The flat on the adjustment rod is also exactly 5 mm. long , so I would expect a 305 mm. boot to force the heel to slide enough so that the reference mark lands perfectly in the center of the 5 mm. flat spot on the rod. Therefore a 307.5 mm. boot would move the pointer to one end of the flat and a 302.5 mm boot would move the pointer to the other end of the flat, and a 305 mm. boot would be right in the center. Therefore the center of the flat is the ideal position for a 305mm. boot, but the heel binding will tolerate plus or minus 2.5 mm.
Unless you buy a boot whose sole length divides evenly by 5 mm., you will never have your reference pointer in the center (optimal) position on the flat.
So with my 307 mm. Fischer ski boot, I decided to turn the rod in order to get my reference pointer to land on the center of the flat.
Why shouldn't my odd sized 307 mm. Fischer boot benefit from the same optimized forward pressure as the 305 mm. Nordica boot? My binding now behaves as if I am wearing a 305 mm boot with my plates dialed in for 305 on the scale.
Of course Nordica wanted the CT system to cover a selective range of boot sole lengths without the need to fiddle with fine adjustments.
For my 2009 Nordica non CT plate system with Marker bindings, there is a similar forward pressure adjustment, but instead of a 5 mm. flat on a metal rod, there is a 4 mm. triangle with scribe marks in the plastic triangle. I fine tuned the Marker forward pressure so that the reference pointer is in the center of the triangle.