The Board of Immigration Appeals has determined that the written frivolous warnings on the I-589 application are sufficient to give notice of the consequences of filing a frivolous asylum application. There is no requirement that a judge provide oral warnings and withdrawing the application does not preclude a frivolous finding.
The full text of Matter of S-M-H- can be found here: https://www.justice.gov/eoir/media/1425081/dl?inline