The limitations of Esri File Geodatabase support is as follows

• Subtypes are registered as a single feature with a domain containing the subtype values. Property based symbology rules can be used to differentiate the subtypes.
• Feature data sets are registered as separate features.
• Domains are supported only as coded value domains.
• Relationships that can be modeled as sub features are supported. However, support is read-only. Features involved in relationships cannot be created, updated, deleted, or exported.
• Annotation sub features are not supported in the Esri file geodatabase due to limitations of the API.