Quiering Write Concern values

When I am querying Write Concern on the client - specifically calling mongocxx::client::write_concern() from a C++ code, when Write Concern was not explicitly defined for this client, I receive majority = false and number of nodes = undefined. As far as I know write concern should be majority for the replica set I work with; so the question is - does the function return write concern that is currently set for this client (or database, or collection) or it shows what write concern will be if I perform an operation with client (or e.g. database) and won’t override it on the lower levels (e.g. for specific operation)?