If you read the report it talks about a lack of affordable housing, and thus people living 20 to a house, alongside outlining the other reasons that make it inhumane. Am I wrong to infer mass immigration into a housing shortage holds no relevance to this issue?

Here's the report:

https://www.ohchr.org/sites/default/files/documents/issues/slavery/sr/statements/eom-statement-canada-sr-slavery-2023-09-06.pdf

Here's the Bank of Canada on immigration relative to housing:

But there have been hiccups. Canada has long had housing supply challenges. The recent increase in newcomers has coincided with those material supply issues, raising questions about how chronic housing challenges might limit Canada’s future growth and what the implications are for inflation.

https://www.bankofcanada.ca/2023/12/economic-progress-report-immigration-housing-outlook-inflation/