There are people with precarious immigration status who have filed and are waiting for a claim to come through. Their immigration claim has been denied, but they cannot be deported, because the Government of Canada has deemed their home country too dangerous, so they don't have anywhere to go. There are people who are in limbo because of their precarious status. It is not a large number of people, so it doesn't cost a lot of money. In that category, they are considered residents under the Income Tax Act, so while they are waiting, they are here, they are working, and they may be having more children born in the country, but they are still denied the Canada child benefit.
Repealing that section in the Income Tax Act, which is arbitrarily making that eligibility requirement, would not have a very big cost in the federal budget, but it would have a very deep impact for these families who are dealing with many health-related and other issues.