No, growth walks around the town, over the roads, untill it finds an open spot to build on, if it takes too long to find a spot, it will skip building that day and tries again next day. In huge cities like that, it happens often if you don't watch out, so you disconnect roads that have no open spots left, so that growth doesn't go there.
As far as I know completely removing roads isn't needed, but cities do sometimes build on places where there's no road, although it's rare.
By removing them, you create some extra space where the intersections used to be though, and while you're removing 1 piece of road on both sides, you might as well drag over the entire road.