are multiple triples forbidden in @id?

[VladimirAlexiev]

https://json-ld.github.io/json-ld-star/#example-embedded-node-as-subject:
If I add another key (eg sex) inside @id:

  "@id": {
    "@id": "bob",
    "age": 42,
    "sex": "Male"
  },
  "certainty": 0.8

1. Is that forbidden (where does it say that?)
2. Or does it duplicate annotations like:

<<ex:bob :age 42>> :certainty 0.8.
<<ex:bob :sex "Male">> :certainty 0.8.

As you can attach lots of annotations, such duplication would seem ill-advised.

[gkellogg]

From the Draft Spec, an embedded node describes exactly one property/value pair; effectively a single triple.

Embedded Node
An embedded node is a node object describing exactly one property/value pair. The node object MAY be identified as with other node objects (including with an embedded node). The property MUST be either @type or an IRI. The property value MUST be either an IRI, blank node, literal or an embedded node. An embedded node MAY contain other entries that do not, themselves, create directed-arcs, such as @context or @index. An embedded triples is the representation of an embedded triple.