People with severe mental illness are hard to live with. When I was growing up there was a homeless man who spent all day at the public library that people called "The Professor" who was said to be unable to live indoors because he'd wake up screaming every night. We took in a friend who I think had schizoaffective disorder in and she threatened my wife with a knife after she'd lived at our place for 18 months. Schizophrenics are more likely to be the victims of crime than the perpetrators but every so often they do something that is "batshit crazy"
https://www.mlive.com/news/muskegon/2017/11/look_back_thanks...
"Housing first" is an improvement over the status quo but people with severe problems are going to make that kind of environment hard to run. "Dispersal" may very well make it possible because that kind of behavior randomly scattered won't break people's ability to cope with it down, whereas concentrating it in one place certainly does. I can't see how anybody who has any moral sensibility at all could stand to go to SF, never mind live there. Just as the rationalists try to break down our moral sensitivities by spamming us with trolley problems, exposure to that filters for a population of people who just don't care.
BTW, the one way bus ticket was tried in SF long ago, just like they've tried the other obvious non-solutions, but they came to the conclusion that the offer of bus tickets away just made it more attractive to go there.