Boolean property values have to be queried in upper case
When querying with Boolean properties, the values have to be provided in all-capitals, otherwise they are not recognized.
E.g., on demo.indiscale.com, log in and trigger the crawler, then execute the queries
FIND ENTITY WITH generated=true,
FIND ENTITY WITH generated=True, and
FIND ENTITY WITH generated=TRUE. Only the last one will return non-empty results.