I was just curious, reading this post, so I took my EF 400mm f/2.8 L IS II and slammed it in the ground (it's a mixed stone-marble ground, not so sure about its Young modulus). It still worked fine.
So I went out and found a more defined surface, made of concrete (25 GPa modulus), and made something more serious (I hate answers based on "I think" and "maybe", like "it bounced on rock and Landed on mud"), dropping it vertically (front element facing the ground) from 1 meter.
Still perfectly fine, just few scratches.
Since a single test is not representative, I would suggest that we all do the same, and collect data on a statistically significant number of specimens.
Just my two cents.