In some senses, I think the government took a very prudent approach originally, because there was a relatively short time frame between the completion of the multilateral convention and the initial signing ceremony and there was a desire to ensure that there would be sufficient time to appropriately review the treaty network to ensure that implementing such a provision through the MLI would be appropriate in all of the treaties that were likely to be covered, and also to have some time to ensure that the Canada Revenue Agency thought they could administer it.
On February 5th, 2019. See this statement in context.