I think this is the part of housing policy that is easy to miss from the outside: a lot of apartment projects are already right on the edge.
Nobody builds rental housing just because it would be nice to have more of it. The land, financing, approvals, construction costs, vacancy assumptions, and neighborhood politics all have to barely work together. Add one more big source of uncertainty, or a tax that hits at the wrong moment, and some projects quietly stop happening.
That is the sad part. A policy can be aimed at very expensive property, but if it scares off new apartments, some of the cost ends up landing on future renters too.