The problem is that we are such a small number of cases to draw observations from.

Nobody here really knows exactly what triggers the SSSS algorithm - or, if they do, they've decided not to jeopardize their security clearance by posting it in public - but given the inconsistencies we have seen I'd bet that it's a weighted equation that includes factors other than just one's itinerary and I don't think we are certain at all that PreCheck may not reduce the probability or intensity of SSSS spells.

I've noted in other threads that I got hit pretty hard by the CBP, including pre-boarding visits from the Immigration Advisory Program. (Slightly OT, but it's been a bit of a relief to finally see reports this spring of other USC's getting mysterious CBP pre-boarding interviews that sure sound like IAP such as described here - I don't feel quite so crazy anymore!) Despite the rough receptions I've gotten from CBP, my SSSS flag has always worn off in 0-3 check-ins after leaving Turkey. I'm very open to the possibility that I seem to be getting fewer SSSS's because my PreCheck enrollment is considered an attenuating factor by the TSA and/or the National Targeting Center.

It's also rather curious that an entry that doesn't seem to attract the wrath of CBP can result in SSSS on domestic flights down the line, and vice versa - I just did a pretty "broken" itinerary Istanbul-MUC-LHR-YVR followed by a bus crossing at Blaine, WA last week, absolutely no questioning or harassment at any point in the trip, and now I can't check in online for my flight out of SEA tonight... *sigh*