Thanks for the insights. Essentially the reason for embedded data sources is that the elements using them are being copied and pasted between reports; and they need to bring the data and calculated fields with them when they travel. You mention custom field IDs, and yes, those are in place in all the data sources so cross filtering is not an issue. The 5 Looker Studio data sources in my theoretical example would all pull data from the same view that we built in BQ (there aren’t any Looker Studio custom queries) but may have different source-level calculated fields (done in the Looker Studio data source).
In my use case, it’s just a lot simpler to manage and implement if there are separate embedded data sources that use the same BQ view, so I’m just trying to figure out if there’s any huge downside.