Well said. Thanks for writing this up. I agree with you. I also made a lot of comments in the 2.1 Working Concepts document. But I will add them here for community discussion.
Some people have stated that the follow are PROs for using an SDO... Here are my comments to them
1) Better correlation across reporting (you can re-use the UUID, tracking targeting of locations over time)
Bret: Nathan's comments in email suggest that is not actually a benefit but rather a false benefit as there would be no way to actually reuse outside of a single system and STIX is not able a data model for a single system but rather a data model for exchange.
2) More flexibility in adding new relationships...I can add a relationship saying that your target identity is located in US, don't have to issue new identity
3) Ability to define a single location shared across multiple objects that occurred or are relevant to that one location without having to copy either coarse or fine-grained location multiple times
Bret: I do not think this is a benefit. The overhead of creating the location SDO and all of the needed relationships would actually be a TON more work and overhead than just embedding the data.
4) More natural uses of the STIX graph model
Bret: But you could argue then that everything or most things should be SDOs, like Nathan mentioned in his email, why are not Goals and Motivations also not SDOs
5) Less updates to the core properties of an SDO, if a location for a particular entity changes
Bret: I do not think this is really valid.