on the phone's site "The drop test. We drop tested the Essential Phone on solid concrete to ensure that your phone could survive a bad accident. See it in slow motion." On Gorilla's site "devices were dropped face-down from 1.6 meters onto rough surfaces. Gorilla Glass 5 survived up to 80% of the time, far outperforming competitive glasses. "...stupid companies with lie marketing, this phone's screen broke from knee height on first drop! This is worse than the most fragile phone from this year, Galaxy S8. The Essential Phone started as a great idea and ended up as this year's biggest disappointment (worse than HTC U Ultra, which was a nightmare).
Which means the repairability score is ner 0/10 since the back cant be broken off
No, the premise is correct; Ceramic is quite brittle.
There is always an explanation for results like this.
These drop tests aren't controlled in a scientific experiment, and when tested as such, we can gain further data.
A better back material still is Metal, Leather, or Polyurethane.