Jung as (a) thinkerWhereas the indefinite article is required in the previous examples, there isvacillation in the following cases (cf 'unique role', 5.42):her duties as (a) hostessmy appointment as (a) lecturer
A Comprehensive Grammar of the English Language
Why does the writer say there is vacillation in the cases with the complements?
Is there anything different between the previous one and them?
Is the reason that they refer to persons?