SYSML2_ — Explanation for extended-usage and extended-def concepts

In the GBNF 8.2.3.6 Definition and Usage Graphical Notation (pages 192-195) of the SysML v2 Specification, the "extended-def" and "extended-usage" concepts are introduced without any explanation of what they represent—whether they refer to a usage/definition annotated with any metadata, semantic metadata, or something else. This is important because "extended-def" and "extended-usage" have dedicated symbolic representations, as shown below (simplified):
extended-def-name-compartment ='«' DefinitionPrefix 'def' '»' definition-name-with-alias
extended-usage-name-compartment ='«' UsagePrefix '»' usage-name-with-alias

To sum up, this symbolic graphical representation allows only annotated metadata within guillemets to be displayed, while omitting the metaclass name. During the OMG Graphical Specification meeting, it was highlighted that extended usage and definition should only be interpreted when annotated with SemanticMetadata rather than any Metadata. However, this is not documented anywhere in the SysML v2 specification.