The warranty has always covered a single hairline crack.
If there are multiple cracks, chips, or a POI on the outside of the glass. It's clear as day what happened to the screen.
I can't count on my hands or toes how many people will say they don't know what happened to the physically damaged machine. Maybe someone else broke it and they didn't know. But I can tell you that we fix more physically damaged machines than we do single hairline cracks. So I would say this isn't a huge issue that people make it out to be.
I think it's more plausible that people are surprise that their really expensive super thin and sleek computer breaks when it's physically damaged.
To me the super thinness out right screams to being part of the cause.
Without taking one apart to confirm it for myself, going off past patterns I would guess Apple have thinned the lid and the display past its limits under every day use (not lab conditions). Pair that with People having got used to using a single hand to open/close their screen, heck even Apples marketing pushed one finger lid openning/closing. So people are not closing their screens "carefully" from both sides with two hands any more (and haven't been doing so for many years, as its easier to close a laptop lid than open it).
But with thinness comes lack of rigidity, so closing the screen with a single hand unless you do it smack bang in the middle I would guess is putting more strain on one side of the lid leading to a premeture screen failure.
Basically "Bendgate" all over again.
But its not the first time we seen screen issues on macbooks come to light once the devices where in the hands of real world people. Look at the stage light defect which for the longest time Apple denied as a fault https://support.apple.com/en-gb/13-inch-macbook-pro-display-... which turned out to be that the flex cable was just a smidge too short and repeated normal use damaged the flex cable.
I'm not saying the customers are not at fault. <edit>Heck I've seen plently of dropped devices and the customer swears on their first born they didn't do nothing. Until you point out the impact damage and suddenly it all comes flooding back to them.</edit> I just see a repeating pattern and would like to dig into it more before I dismiss the customer saying they don't know what happened.
The tight closure with just about zero clearance and no bezel is a significant part of the difficulty.
Anything in there, even being closed gently and you notice at the first sign of resistance and correct it - has probably cracked the screen.
Charger/cable/pen tip is common, but even a paper clip could be enough. There's no audible crack and you think nothing of it until the next time you take it out of your bag and the display is broken. That said, this sort of thing will typically have a point of impact/multiple cracks, not just one straight line.
Plastic webcam covers will also do this, just less consistently - they hold the display open a bit and concentrate all the force of the closed lid there.
Perhaps they were intending on keeping that a customer responsibility for the comment above yours.