I've certainly seem FAs and GAs tell people that their connections will be held (HA!) but an outright specific lie saying that you've been rebooked onto a specific flight seems like a particularly extreme and potentially harmful version of this. In particular, if the passengers had assumed that their first connection reservation had been cancelled and they were confirmed on the later flight, only to stroll to the gate for the later flight and learn that they had missed their flight and there was no space later that day, it would have unnecessarily been extremely inconvenient.