The two measures are closely related, in a way. My impression is that it depends a bit on the speed at which housing starts can take place. There is a reaction time that can, in the short term, affect demand more than supply. Of course, in places like Vancouver and Toronto, there may be more constraints and administrative delays in terms of housing starts. There are not only physical constraints, but also administrative delays related to the approval of the various levels that can come into play.
So, in the short term, the measures could have a greater effect on demand than on supply. Naturally, in the long run, the two will interact. There will be price expectations, which will also have an impact on supply, but in the short term, in some markets at least, there will probably be a greater effect on demand than on supply, given the time required to approve the plans.