I think the point is that removal of double taxation on non owner occupied residential units should make it more attractive for developers to actually build more rental units.
At the same time, if some form of taxation penalty could be applied to unimproved properties in the core, then it would make it less attractive for developers to sit on their properties and live off of parking revenues.
Knowing Heritage, they are not interested in development anyway, but, this could incentivize them into selling some of their land to an actual development company so that something could get built.