Not sure that will work universally. For starts, ever since airlines started sharing APIS data with governments, full PNR info has been collected for all passengers. Consequently, stamp or no-stamp, there's a possibility that having KRT included in a post-2011 itinerary might eventually result in auto-cancellation of the ESTA.

The real problem isn't so much explaining the trip to a CBP officer upon arrival as it is getting on the plane in the first place if one's ESTA is unexpectedly voided by an automated batch-process.

There's really no telling how these new provisions will be implemented in practice - but given the stories one hears of totally law-abiding people being arbitrarily prohibited from travel (sometimes even after check-in), it's not impossible these new regulations might have some nasty unintended consequences for Flyertalkers.