It's becuz of the symptomology, that's what bumps u up. Passive suicidal ideation, irritability with unproboked periods of violence, obsessive rituals (which can be anything like repeatedly checking locks on everything & not going to sleep till u do, or cant leave house until u make sure everything is secure, etc) can bump u up to 70 as well. Neglect of hygiene, hallucinations, weird speech etc can get u bumped up to 100% sometimes. I'm not advocating this, mind u, just saying. I DO see that suicidal ideation was mentioned however u stated it's rare & u denied it on exam, hence why it wasn;t checkmarked. Same thing with "shutting down" & not taking care of hygiene...it's not constant, therefore why it's not checkmarked.
If you have other conditions that are service connected that also contribute to your inability to work & they equal a combined 70% you can still qualify for unemployability.