I was reading the documentation on Diagnose Data Discrepancies in CJA. Here is the URL (Customer Journey Analytics FAQ | Adobe Customer Journey Analytics) and screenshot below.

What is confusing me is how the example is worded. If someone deleted the data set from AEP, then the data set should be deleted from CJA. Deleting a dataset in Adobe Experience Platform data lake stops data flow from that dataset to any Customer Journey Analytics Connections that include that dataset. Any data from that dataset is automatically deleted from the associated Customer Journey Analytics connections. What am I missing? Shouldn't CJA only have the single data set?
Thanks!