**Found this explanation on Youtube**
If there had been no space there, the glass would've hit
the stainless corners and get crushed by them when
the phone got hot. This is something that atoms do,
the space between them increases when they are
heated, making the matter have more volume than in a
colder environment. A paper is approximately 0.01mm
thick, so 1/10th of a millimeter. That gap is there to
prevent the phone's glass from breaking suddenly
when you're in the beach :D There is also a sticky
frame seal around the iPhone to keep it waterproof.
With the pressure the top panel makes, you cannot
break that seal from outside just with a piece of paper.
Please stop inventing gates by yourself, also the green
tint issue will probably be solved via software update
and if it's a hardware issue, Apple would gladly replace
them. I have seen this screen flickering "issue". It's the
nature of OLDs' brightness control mechanism
(called PWM), and cannot be seen by the human eye. It
used to flicker more and create eye soreness for
1/10th of users, but they've seemed to fix it mostly
since iPhone 11s.
Hope this helps. 🙂