As for the iPhone 8's screen, it's pretty similar to the glass back, as it can crack from about waist height no matter what angle it drops.
The iPhone 8's front screen can also crack from a waist-level drop, so it's worth getting a case to protect to protect the screen in the first place.
From the drop tests, it looks like the iPhone 8's glass back could potentially survive a waist-level drop, but I'd still recommend using a case.
The iPhone 8's glass back survived two of the YouTubers' waist-level drop tests, but it cracked on PhoneBuff's test. That means the iPhone 8's glass back has the potential to crack from a waist-level drop, and you're better off getting a case to prevent cracking the iPhone's 8 glass back.
As you'd expect, the iPhone 8's glass back isn't as durable as the metal back on the iPhone 7. Still, you were better off using a case with the iPhone 7 to protect its screen from a drop.
And the glass backs on both phones cracked.
The drop's height isn't clear from PhoneBuff's video, but it looks like it could be between three and four feet, which is similar to a waist-level height.
And finally, tech YouTube channel PhoneBuff dropped both the iPhone 8 and Galaxy Note 8 on their backs.
Dropping the iPhone 8 a third time on its side finally cracked the iPhone 8's screen, but not its back.
And the iPhone 8's glass back still survived, much like the iPhone 8 Plus did on EverythingApplePro's "pocket height" drop test.
Zack from the JerryRigEverything YouTube channel performed a second drop test from waist height and found that the iPhone 8's glass still didn't break. It's looking pretty good for the iPhone 8's glass back so far.