So I did some more digging around with the numbers and came to the conclusion that this is probably a bug or a feature that is implemented backwards. Basically what seems to create the problem is the "Photo Border" feature. When you add a border the image in Lightroom gets scaled down to compensate and that is what Lightroom displays. When printing however, the image is scaled back up to the size of the frame and the border is now masking it. Here are some images to demonstrate this:
The original image:
The way Lightroom displays it when the border is added:
The way Lightroom prints it:
What actually goes on (masking instead of scaling to compensate for the border):
Has anyone else run into this or can confirm that they get the same behaviour on their end ?