Deserialization fails, if the schemas attribute contains an extension schema, but no data is contained in the JSON object. The SCIM spec states under https://tools.ietf.org/html/rfc7643#section-3.3
Each value in the "schemas" attribute indicates additive schema that
MAY exist in a SCIM resource representation.
This means, that the presence of an extension schema in the schemas attribute, does not necessarily mean, that the current JSON object contains data for this extension. So, the restrictions of the user deserializer have to be loosened.
Deserialization fails, if the schemas attribute contains an extension schema, but no data is contained in the JSON object. The SCIM spec states under https://tools.ietf.org/html/rfc7643#section-3.3
This means, that the presence of an extension schema in the schemas attribute, does not necessarily mean, that the current JSON object contains data for this extension. So, the restrictions of the user deserializer have to be loosened.