Understanding QueryOutputFields and QuerySelectedFields
If you select a field from a Query Record, it becomes a QueryOutputField, that is, it becomes one of the columns in the SQL output. QuerySelectedFields consist of displayed fields and Query Expression Fields.
QuerySelectedFields and QueryOutputFields have all the same methods and properties, so in this documentation, they're described together under the heading QueryField.
The collection of QueryOutputFields does not necessarily include all columns returned in query resultset. This collection only includes columns that have been added to query output collection using the query classes or by an end-user designing a query.
PeopleSoft Query can also add additional columns for related language processing and also for translate labels on fields, and so you cannot use the Query Output Collections as a way to discover all of the columns that are returned in the resultset or by executing the SQL generated from a query.