I don't care if they can shed a lot more than that. I'm saying it needs to at least match the XPS.Not really, the current retina MacBook Pro was released in 2012 and was(and still is) 18mm thick.
The Dell XPS 15 InfintyEdge or whatever it's called was released 7 months ago and is 17mm thick.
Apple can easily shed a lot more than that as shown with the new Macbook which is only 13mm thick.