We have a complex schema setup whereby we have a list of components of different types, which then have a set of properties that are reference types - again of different types. So, Block 1 has a list of types such as image/text/document/menu/article etc. So, the block could have a lot of different schema types as its content.
When retrieving from the API we just get the guid for the reference item. Without knowing the schema of that object we have no way of retrieving the details for it. If the API response contained the schema then we could retrieve the correct reference.