I can't say specifically with that project, but in general I think the tactics that are used are to try to suggest either that a building is too high or that the surface area coverage is too much in an attempt to effectively reduce the number of affordable homes that can be in there.
Another one would be to push for underground parking as opposed to above-ground parking, which effectively will reflect on the feasibility of the building, forcing you, from a pure economics perspective, to have a higher mix of market-affordable rent.