Exporting placed PDF files using PDF Passthrough will correctly honour Overprint for PDF/X compliant files but ignores Overprint for non-PDF/X compliant files (i.e., PDF 1.4, 1.5, 1.6 and 1.7).
Exporting placed PDF files using PDF Interpret ignores Overprint for both PDF/X compliant and non-PDF/X compliant files, i.e., all PDF Formats.
07. pdf_1.7_passthrough_export.pdf
07. pdf_1.7_interpret_export.pdf