overprint simulation of spot colors - change from 9.16 to 9.19?

Dear list members,

today I tried my proven commands for rendering a CMYK TIFF (tiff32nc) from PDFs containing overprinting CMYK and spot color elements.
v9.16 creates a correct CMYK comp representation with overprint simulation of of both - v9.19 does not simulate the spot color overprints.
Following commands work flawlessly with 9.14 and 9.16:

/usr/local/bin/gs -dSAFER -dBATCH -dNOPAUSE -dNOPROMPT -dUseMediaBox -dAlignToPixels=0 -dGridFitTT=2 -dTextAlphaBits=4 -dGraphicsAlphaBits=4 -dSimulateOverprint=true -sICCProfilesDir="/opt/local/share/ghostscript/9.19/iccprofiles/" -dUsePDFX3Profile -dRenderIntent=1 -dBlackPtComp=1 -sNamedProfile="/Volumes/XYZ/GhostScript_ImageMagick_PDF2JPEG/spotcolors_lab_values.txt" -sDEVICE=tiff32nc -r200 -sOutputFile="/Volumes/XYZ/GhostScript_ImageMagick_PDF2JPEG/output_%03d.tif" "/Volumes/XYZ/GhostScript_ImageMagick_PDF2JPEG/input.pdf"

Just a note:
I am using my own named color table to get better spot-to-CMYK color conversions, entries look like this:
4357;
PANTONE 100 C, 92.040, -7.560, 65.760;
…

Screenshot of both results is attachment. If attachment should get scrubbed by list, here’s link including the source PDF: http://kurz.link/3hY

Does anybody have an explanation for this change in behavior?


Thanks in advance,
Ulf Wittenberg