Secondary indexing on meta().flags and meta().type does not work

When I try to create an index on .flags or .type i get the following error

RUN QUERY CREATE INDEX idx4 on default(meta().type)

u'errors': [{u'msg': u'Expression not indexable: (meta().`type`) - at )'

However this documentation 

https://docs.couchbase.com/server/5.5/n1ql/n1ql-language-reference/indexing-meta-info.html

Seems to imply these fields should be indexable, is this expected behavior and the documentation is wrong, or is this incorrect behavior. I have 10 binary documents in my bucket created by cbworkload gen

Please close out if this is expected behavior