CMYK to RGB export should always translate 100K to RGB 0,0,0
As per the title, when working with a CMYK document with 100K blacks, when exporting to RGB, these should always get translated to RGB 0,0,0 - regardless of what Printing/Exporting setting is used in the Appearance of Black preference menu.
Right now, when exporting a CMYK document to RGB (regardless of whether you use PDF, PNG or JPG), if your Appearance to Black Print/Export setting is set to "Output All Blacks Accurately", you will end up with incorrect black levels. What really should be RGB 0,0,0 ends up being RGB 35,31,32 or so. This is true even when working with 1-bit bitmaps (which are nothing but pure black & white).
This can be fixed by changing Appearance of Black - Print/Export to "Output All Blacks as Rich Black" - blacks end up being proper RGB 0,0,0 black - but it really should work like this regardless of what the Appearance of Black settings are set at.
A couple samples:
"Accurate" blacks PNG: https://my.mixtape.moe/metyyt.png
Rich blacks PNG: https://my.mixtape.moe/bpgnib.png
"Accurate" blacks PDF: https://my.mixtape.moe/qjqcfv.pdf
Rich blacks PDF: https://my.mixtape.moe/rrhaig.pdf
Again, the "accurate" black exports should really look the same as the rich black exports by default - black should be proper RGB 0,0,0 black, instead of somewhere around ~32,32,32.
Forgot to mention that this issue is not unique to InDesign - Illustrator has the same problem as well.