You make a lot of assumptions without knowing any of the facts.
As for people crossing tiers, no-one said it was the right thing to do. The suggestion that many are northerners is still valid. You have absolutely no idea of their situations. Some could be students who were living in halls and had nowhere else to go, some may be here for work etc..
As for relatives coming south to get out of restricted areas up north, I cannot see what point you are making and on what basis. Are you suggesting people from the North are less likely to go to areas with less restrictions? If so, would like to know the reason. One thing I know, from actual experience of living in other cities rather than some prejudicial BS, are similar where ever they are from.