hello sgwrx!
Did you discover anything further about this?
I have noticed a similar peculiarity too. In Capture One Pro v9.0.3 I am set to preview/soft proof selected recipe, in this case 16bit ProPhoto. When opened in Photoshop, with no colorspace conversion (the file opens as 16bit ProPhoto) the file looks and prints differently. It is posterized slightly in deep dark tones. The version in C1 is not. I need to test further, but wondered if anyone else has had this behavior. This behavior is mirrored in the test prints, not just the display.
I will test further, but I found it unexpected in the way I understood how C1 and PS worked with color management. If I am seeing ProPhoto in C1 and open into ProPhoto in PS, is it normal to expect small subtle shifts?
Welcome any insight from others too, thank you +
Sean.