This is a very good question, Gabrielius.
I don't know if it's stated explicitly anywhere, but to me it makes sense that the expand directive only works against EntityRef and any refererence that derives from EntityRef and only adds properties that in the entity's schema. For example ProductSpecificationRef has an extra property version, but that's OK because ProductSpecification itself has version.
But in POP relationship, your example, there is extra information in the relationship class itself (role, relationshipType), and it's not so obvious that it is semantically correct to replace the reference by the full class.
Hope it helps
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Jonathan Goldberg
Amdocs Management Limited
Any opinions and statements made by me on this forum are purely personal, and do not necessarily reflect the position of the TM Forum or my employer.
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