请教：OG-19(紫) in that的用法

159. While depressed property values can hurt some large investors, they are potentially devastating for home-owners, whose equity—in many cases representing a life’s savings—can plunge or even disappear.

(A) they are potentially devastating for homeowners, whose

(B) they can potentially devastate homeowners in that their

(C) for homeowners they are potentially devastating, because their

(D) for homeowners, it is potentially devastating in that their（A）

(E) it can potentially devastate homeowners, whose

答案说B中的in that their-- “wordy, awkward, and ambiguous” 为什么呢？

记得以前新东方老师说in that >because, 不是说明in that是个表达原因的很好的短语吗？