Intendend behaviour for setting `@list` in Context but using set objects as values

[WhiteGobo]

What is the intended behaviour, when using a term definition, that associates the term with a list but then use a set object as value? For example this jsonld data:

{
  "@context": {
    "nick": {
      "@id": "http://xmlns.com/foaf/0.1/nick",
      "@container": "@list"
    }
  },
  "@id": "http://example.org/people#joebob",
  "nick": {
    "@set": [
      "joe",
      "asdf"
    ]
  }
}

In the jsonld playground, it just uses the set object as list object(permalink to playground):

{
  "@id": "http://example.org/people#joebob",
  "http://xmlns.com/foaf/0.1/nick": {
    "@list": [
      "joe",
      "asdf"
    ]
  }
}