I think the big message behind Abundant Housing Vancouver is that
1) more housing starts of all kinds (condo, townhouse, rowhouse, etc) is badly needed to help satisfy demand to drive prices down. Since 80% of the land is already taken by 20% (not quite the right numbers but illustrative) of the population (ie in SFH)
2) there needs to be rezoning to make a variety of densities and types to address pricing.
1) Vancouver is already building housing as fast as it can be built. Every year over 30,000 individuals are added to Metro Vancouver's population. In fact the pace of construction is also partly responsible for the increase in housing costs due to labour costs, the supply/demand of materials, delays due to labour issues, the cost of development land due to demand, etc.
2) municipalities benefit financially from up-zoning to a higher density or a more lucrative land use, or subdividing a property. This makes properties more valuable, thereby raising property taxes. A subdivision will also yield municipal costs known as Development Cost Charges which are very, very high.