It most certainly has, but might not have been publicised. I remember some noise about iPhones screens failing in more or less exactly the same way ~10 years ago. These things are bound to happen regularly, but we don’t hear about it. Ion-exchange strengthened glass is resistant to microcracks, but even so fracture happens.
> The corners of my 2012 are noticeably deformed from impacts and the screen is fine
Glass is an interesting material. It can bend and deform in the right conditions, and shatter in others. Your experience would show that the screen is actually well designed (my 2015 MBP had also a deformed corner after having fallen open from a table; I was actually pleasantly surprised that the hinge survived).
I find it a bit laughable that they can "verify it under a microscope". The glass is present under tension, and a weak point releasing that tension could very well cause local divoting at the origin of the crack as the pressure is released towards that point and microsharding occurs.
Your counterexample means even less, since my numbers are based on measuring something useful.
Besides which: what kind of case do you think you're making by pointing out that actual design/manufacture problems with Apple products show up in Apple forums?
How else would it be?