It has more to do with provinces that require the amount determined in paragraph 122.61(c) of the Income Tax Act. If they refer to needing that information specifically, then with the change in the rules, (c) wouldn't have been there anymore. It was kept on the books for a couple of years to give provinces an opportunity to transition their information requirements to the new Canada child benefit system.
On April 24th, 2018. See this statement in context.