I think that after reading that guidance, you'll agree that FinCEN wasn't willing to draw a bright line around circumstances that would trigger your having to aggregate across ownership of separate entities. It's one of those "facts and circumstances" things that FinCEN expects you to figure out based on your knowledge of the customer(s) and their actions.
Analyze the information you have carefully, and obtain whatever additional information you can about the businesses. Then make your determination. Document what you've done, and be ready to defend it if an examiner decides to try second-guessing you.
John S. Burnett
Fighting for Compliance since 1976
Bankers' Threads User #8