Scale is hard to judge, but my gut sense is that land per unit is at least double in that listing—these units go back pretty far to make up for minimal street frontage.
Housing units is what matters for solving homelessness, not number of people housed. These tiny homes aren't intended to house whole families. Yes, you could fit 8 to 10 unrelated homeless people in a single family home or townhome, but there's a reason why that's not pushed forward as a solution—people don't generally want 9 strangers as roommates.
I definitely agree that the economies of scale that come with the shared walls make a huge difference for general practicality, but I was only speaking of land use per housing unit.
Edit: Here's a link to the satellite image [0] so you can see the depth of the property. The unit alone is about twice as deep as it is wide, and then it has a backyard per unit in addition to that. My very rough estimate with the Google maps ruler suggests about 1000 sqft footprint per unit.
[0] https://maps.app.goo.gl/cqLLmbU3Rtufkfx78