The 'glue' in retina displays (based on my experience with the iphone 4's lcd) fuses the front glass to the LCD screen. Usually you can separate the protective glass and the LCD screen, but not on a retina display. That is why if you crack the glass in front of an iPhone 4's LCD, you have to replace the entire LCD (~$70) and not just the glass (~$10).
That’s what I tried to explain. There is one less protective layer in the Retina MacBook compared to other MacBooks – but the same amount of protective layers compared to matte MacBook Pros. I don’t think it makes a difference.
In the Retina MacBook Pro the glass is an integral part of the display, not some separate piece glued on just cause – as far as I understand it. If it weren’t there, there would be a piece of plastic glued to the display. (And since LCDs already contain glass elsewhere I don’t think the extra glass changes the equation much.)
