What would be the purpose of putting all datastore entities in a single group?

Question

I have started working on an existing project which uses Google Datastore where for some of the entity kinds every entity is assigned the same ancestor. Example:

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Answer 1

This was probably done to achieve strongly consistent queries within the group. As you've pointed out this design has... drawbacks.

If this is solely reference data (i.e. Read many write once) that may mitigate some of the negatives, but also mostly invalidates the positives (i.e. Eventual consistency is not a problem if data doesn't update often).