DJ IN clause not supported when utilized with another clause

http://idm.example.com:8080/openidm/managed/user?_pageSize=1000&_fields=preferences&_queryFilter=userName IN '["user0a"]' 

http://idm.example.com:8080/openidm/managed/user?_pageSize=1000&_fields=preferences&_queryFilter=userName IN '["user0a"]' and true

{
    "code": 400,
    "reason": "Bad Request",
    "message": "The query request cannot be processed because its query filter '(/fullobject/userName IN "[\\"user0a\\"]" and true)' contained an unrecognized or unsupported filter operator 'IN'"
}