I wouldn't have said it that way. What happens is that, if you are a senior in Canada, you get partial OAS if you don't have 40 years of residency in Canada. All seniors who are immigrants are going to get reduced OAS if they have been here less than 40 years. If they are also on GIS, then the GIS will replace their missing OAS. Canadian-born people are going to get full OAS. You've brought the immigrants up to what Canadian-born people would get if they are poor, so I don't think the immigrants are getting something Canadians don't get.
I don't know if I have any time to talk about GIS clawback. I have some ideas.