This isn't unique to v2, this has, as far as I'm aware, always been an issue in all versions of Publisher...
When placing a PDF file in a Publisher document, text that uses the same colourspace as the document colourspace is incorrectly flagged as a preflight error with the error/warning...
Placed PDF has objects of a colour different to the document colourspace. The PDF will still pass through.
When objects using the same colour definitions are used in place of text, the preflight error doesn't occur.
When PDF Interpet is used, the preflight error doesn't occur but at the same time in v2 versions of Publisher, the Placed PDF doesn't redraw, i.e., it vanishes from the canvas which I believe is a different, but already logged bug.
PDF Text Passthrough.mp4
Files attached
Source Designer File
Source Exported PDF 1.7 files
Publisher Document with Placed PDF 1.7 files using Passthrough...
Note: The font used is Lato Bold, available as a free download from Google Fonts.
Preflight Error Bug.zip