The way KLM has operated with these tickets to date was built around the requirement that the customer, if challenged, had to provide positive proof by showing their stamped train ticket. It was never about KLM proving the customer didn't travel - it was all about the customer proving that they did travel. Absent that proof, check in could be denied.

I find it hard to believe that KLM suddenly had a change of heart and now just accept it as a given that anyone showing up at the check-in desk at AMS has used their train segment.

Which is why I am wondering - is there some new digital system that will alert the AMS check-in agent if the barcode/QR code wasn't scanned on the train by the train manager? And even if so - isn't the customer's cancelled train ticket the simplest, and most reliable, proof?

(Again, I really have a hard time believing that KLM have instantly dropped all suspicions regarding these tickets and no longer check that the tickets were used as indicated and, up til now, checked. It might be OK if your FB account is registered in Belgium, for all others....unless there's been a rollout of new fares ex-ZWE which match the prices available from AMS. Perhaps THIS is actually what has happened!. There would no longer be a need to check train travel closesly if the price charged when starting from ZWE no longer represents any savings over starting from AMS!!!)