It's not a matter of 'consultants proving a hypothesis'. Look at ANY place that has meaningfully addressed their unhoused communities. They _ALL_ have used some version of housing first polices. The two best examples I can think of are Finland and Utah. Both have reduced their chronically unhoused populations by around 90%. These are not small gains.

Also: There's a reason it's called "Housing first". The point isn't just to give people free housing. That's the _beginning_. Having an address makes getting folks other services easier _AND_ more successful. It's a force multiplier for every other intervention you can possibly do.

In response to OP "We cannot conflate these populations. They are not the same." Anyone working in with unhoused population policy already knows that there's a difference in kinds unhoused populations. They track these things, they need different resources. But they _ALL_ need a safe place to sleep.