Who even makes that suggestion, anyway?

The article. Just follow the trajectory of what's being proposed.

We remove all zoning restrictions throughout cities that have ever increasing density, and tight greenbelts preventing further expansion. We don't build other regional hubs to connect them to, continuing to drive all regional traffic through these primary hubs that are experiencing ever increasing density and congestion, making it harder to travel around the region, making the hub the only spot that's convenient to live, driving more demand to live there.

Manhattan's density is the end result of a failure of regional planning and runaway feedback loops that have allowed demand for a region to get out of control to the point that they've created literal permanent twighlight at street level.

Now the article does propose capping the limit at 6 stories, which would prevent the full manhattanization of a city, but would instead more quickly lead to a paris or barcelona where all single family homes, be they dense townhouses, or sprawling in city suburban ranches, be torn up and replaced with apartments and condos. Not only will this destroy some of our quite frankly mostly nicely balanced housing from a density / quality of life standpoint (the dense townhomes and streetcar suburbs), but failing to put any controls on how the process of people being priced out of their homes and letting the market do the work is having the impact of shifting more and more power to landlords and corporate real estate which then further extract money from the general public since they have the resources to exploit this inelastic demand.

Again, I'm not saying we don't need to densify, nor that we shouldn't be building a lot more midrises (and even some high rises), but we also need to recognize that virtually every major city in Canada is grappling with a hub and spoke regional model that provides no outlet valves and creates feedback loops driving unsustainable and unpleasant pressure instead of spreading it through a region in a more balanced way and a lot of the calls for complete removal of zoning laws are coming from developers who simply want to build cheap shit to lease back to you at a profit.