I went into the Apple Store and tried this on both the new 13" and 15" models... they all have it. All in all, I've tested personally on over 10 machines and they all exhibit this noise/feeling of the light guide sliding around inside the display. At this point, I'm fairly certain anyone claiming they don't have it is simply in denial - one Apple employee tried it and was like "nah, there's nothing" but then his peers tried it and exclaimed "oh my god, that's definitely moving around!!" but he still wouldn't admit there was something wrong with the machine... so either they're in denial or the light guide adhesive tape is yet to come unglued (it can take a few days/weeks depending on environmental settings and heat the display reaches)
Now to be clear, this issue is also apparent on the 12" MacBook *and* the 2015 rMBP, however it is much quieter on the latter and you can't "feel" the thing sliding around inside, which is what was unnerving for me. I couldn't even tilt my 2016 13" non-TB without feeling the physical shift of weight inside the display. My guess is that it's more apparent as the display build is thinner/lighter.
I've since purchased a 2015 rMBP with maxed out specs, on sale from BHPhotoVideo so got a great deal.