A television, traffic, or somebody else in the room could stop your receptionist mid-sentence. Worse, whatever the noise was mistaken for was then treated as something the caller had said, so the reply that followed could be about nothing at all. On a busy shop floor or from a car, that made calls feel unreliable.
Saying “yeah” or “mm-hm” also stopped it dead. Those are the noises people make while they are agreeing with you, not interrupting you — a person does not stop talking because you said “mm”. Your receptionist now carries on through them.
Interrupting still works, and that has not been weakened. Start a sentence and your receptionist stops and listens, exactly as before. If it does hold on through something and you carry on trying, it always gives way — nobody gets stonewalled. And when it is reading out something you need to write down, such as a verification code, it will finish that short sentence rather than losing it to a cough.