Sorry, Wolfgang - but I’m still not understanding you (which seems like an ongoing “theme”, for us 
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Are you suggesting that it’s a bug whereby the Protect Saturated Colors Algorithm IS applied (with default strength of 50) when the Export PSC setting is selected - even if Soft Proofing is OFF ?
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If that’s it - then I disagree … I reckon that’s correct and an intentional feature.
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But, if that’s not it … then please elaborate for my slow uptake !
Your post highlighted this for me;
'Tis curious that “Red” is noted as “for paper” ?!
Red is used to highlight OoG colors in the destination gamut … but, that’s not limited to printing/paper only (or is it?).
Note: Also see my Request/Suggestion here.
John