Import/Export Site-Specific Attributes
Site-specific product attributes require specific import/export handing, specifically for metadata.xsd and catalog.xsd.
If an attribute is marked as localizable and site-specific, a data error is logged and the attribute is skipped. If an attribute is marked as site-specific, but site-specific attributes are not allowed for the object type, a data warning is logged, and the attribute is imported with site-specific-flag = false.
You can define any non-localizable custom product attribute as site-specific.