Do you have any references that Sweden clusters more immigrants to fewer places than anyone else? Housing doesn't just pop out of thin air. We have 3 cities with over 200k in population. Otherwise top 10 is 100k+. Just last year we took in 100k. Do you expect us to just pop up houses uniformly? One here, one there? Of course clusters build with the magnitudes we take in.
But, that thing you're citing about a limited number of cities that could handle immigration is a good example of why it might be different for Sweden vs Germany.