A market temporarily at 7% vacancy might not have the same deflationary pressure as a market hitting 3% if all actors trust the government will take active measures to keep that rate around 3%. If Montreal added 1000's of units as a one-time deal, some landlords would wait with empty units.

A lot of landlords will keep units empty rather than reduce rent prices and jeopardise mortgages. This is also a big part of why we have a weird commercial market - banks can wait until you get a tenant, but can't accept you signing someone at a lower rate.

Again I really mean what I say: I am advocating for a very long period of extremely high (relative to recent history) vacancy rate. Not a one-time goal.