Restrictions for QUERY export parameter:

The parameter QUERY cannot be specified for full, user, or transportable tablespace mode exports.

The parameter QUERY must be applicable to all specified tables.

The parameter QUERY cannot be specified in a direct path export (DIRECT=Y)

The parameter QUERY cannot be specified for tables with inner nested tables.

You will not be able to determine from the contents of the export file whether the data is the result of a QUERY export.
RTM.