The official plan, which is a written document, doesn't permit a 50-storey tower to be built in Riverdale because it is an established, low-rise, residential neighbourhood. So is Kensington, though it has some low-rise shopping in former residential buildings. The ROM proposal was dropped as a result of wider public, local institutional, and ROM community opposition.
None of these locations are former distilleries, former factories, or a district in need of being revived - in this case with a mix of residential, office and commercial uses. There has been no public outcry as a result of the ongoing development of the Distillery District - including the condominiums built and proposed - which there certainly would be if a 50-storey tower was proposed for the corner of Logan and Riverdale, or Augusta and Baldwin.
Again, the interchangeability argument doesn't hold water.