The obvious question here is why aren't there more reports if this is actually happening on any sort of regular basis? I've been using Google Flights to price DL/Skyteam flights for years now and generally only bring up fares on delta.com when I'm looking to purchase (as I suspect many here do as well). Even when I'm using a companion cert, I first start at Google Flights to get an idea which flights/dates have the best fares. You'd think if this were actually happening there'd be more reports of prices not matching what's showing on Google Flights once you login to your account to purchase. There are also all the OTAs out there where you can do anonymous pricing.