If you go to the actual report[1] instead of whatever this site is, you'll see that question (3.9) was asking where they lived before they moved to Vancouver, not before they became homeless or whatever that site is attempting to imply.

If you scroll down slightly (3.11) you'll see 81% of respondents had a home in Vancouver before they became homeless, which is the data to match the claim ("overwhelmingly people who had stable living situations in those comfortable locations, and became homeless there").

[1] https://vancouver.ca/files/cov/vancouver-homeless-count-2019...