Are extension members allowed in resource objects?

The JSON:API 1.1 specification, mentions extension-members only in the top level document structure (7.1), relationship objects, and relationship links ( But the JSON-example in the “Rules for Extensions” section (5.4.1) shows the “version:id” extension member inside a resource object.

Are extension members allowed in resource objects or not?
If yes, section 7.2 is incomplete.
If no, the example in section 5.4.1 is misleading.

A similar issue appears when it comes to extension members in link objects.
The “Relationships” section ( allows extension members inside of relationship links, but the “Links” section (7.6) does not mention extension members. Does this mean that only relationship links allow extension members but not any other link object?

Thanks for clarification!