Well, it's based on experiences travelling through Germany proper - for example Denmark to France or Italy, including transfers. Often the delay will just be a couple of hours, but then you miss your transfer and you're screwed.
Also if you're on your way to Switzerland the Swiss have no patience for disruptions in their services, so if a train is delayed coming from Germany they're likely to just not accept it into the country at all.
I have also heard from people who were told to spend the night in the train, which DB just parked in the outskirts of the city for the night. That way they could offer passengers a place to sleep in the cheapest possible ways. Pregnant women or families with young children were asked to check in to hotels.