You use some to emphasize that a quantity or number is fairly large. For example, if an activity takes some time, it takes quite a lot of time.
また、4番目の some of 〜の 意味として、 If you refer to some of the people or things in a group, you mean a few of them but not all of them. If you refer to some of a particular thing, you mean a part of it but not all of it.
とあるので、先の例の all buildings ではないが、というニュアンスも入ってるのではないかと 思いました。