Querying inner objects by field name

I'm reading the documentation on this site: https://www.elastic.co/guide/en/elasticsearch/guide/current/complex-core-fields.html#_how_inner_objects_are_indexed

I'm interested in this paragraph:

Inner fields can be referred to by name (for example, first). To distinguish between two fields that have the same name, we can use the full path (for example, user.name.first) or even the type name plus the path (tweet.user.name.first).

so if I have the example from the linked docu site:
{ "gb": { "tweet": { "properties": { "tweet": { "type": "string" }, "user": { "type": "object", "properties": { "id": { "type": "string" }, "gender": { "type": "string" }, "age": { "type": "long" }, "name": { "type": "object", "properties": { "full": { "type": "string" }, "first": { "type": "string" }, "last": { "type": "string" } }

According to the docu I should be able to search with condition last: whatever, but it does not work. I always have to use the full path user.last: whatever. Is the documentation false or my understanding of it? Note that last occurs only in the inner object, so in theory full path should not be necessary to reference it.