[masaegu]

「〜のような特別な事態、状況に身をおいて」と言いた い時に使う。

This sentence means "It is used when wanting to say 'finding itself in a particular state or situation'."

As you stasted, the phrase is used to describe what phenomenon may occur within another larger and more general phenomenon. In other words, it is used to describe a cause and effect.

There is not anything so special about the phrase ～～にあって. I surmise that your book introduces it because it is not a phrase many Japanese-learners are able to use actively. Even among native speakers, it is not something many people use on a daily basis. You will find it quite often in more formal speech, though.

The reason that you find that explanatory sentence difficult would be the very fact that the phrase itself is simple. If you tried to explain the English word "be", you could easily end up using big words, could you not?