Housing size is specifically addressed:
On top of that, the square footage of housing units in Canada has on average been growing across all housing types, which should in theory provide more flexibility for people to live with roommates.
Housing units are bigger and there are more of them per capita any way you slice it: by population, by number of adults, or by number of households.
They make a very compelling argument that the big change is not anything to do with supply, it's entirely a result of easing burrowing standards and increased access to credit. It's not as simple a story, but it actually offers a reasonable explanation for the observed data, while ECON101 Supply & Demand arguments don't match the data. Doesn't matter if it makes sense if it's wrong.