The problem here is, that while affordable housing is a great goal, this is a poor way of getting it. It's not necessary to negotiate for it if you act in a comprehensive way, because you can simply legislate the requirements. Legislating creates a predictable and equal environment for development. Negotiating creates friction, uncertainty and is at risk of being arbitrary. The developers who succeed in such an environment are often going to be that are best at bending the politicians in their favor, both in legal and sometimes illegal ways.
Mayor Lightfoot has the right response here. Spot zoning and using Aldermanic privilege as a negotiating tool are poor substitutes for a comprehensive plan that builds new housing, especially affordable housing.