My testing shows that the activation state of Soft Proofing does matter. If the Soft Proofing subpalette is not activated, but the export ICC profile is “Same as Soft Proofing,” then the amount of PSC applied on export is 0 (regardless of what the slider in the Soft Proofing subpalette is set to). In my test, what I saw on screen with Soft Proofing disabled is what I got on export. I don’t know if that’s always the case (if you have very saturated reds, blues, and greens), but it was in the test I tried.