The charge pump stage is also 2-phased, interleaved, and presents to the input almost 100% duty cycle. Compared with a traditional buck regulator, where the duty cycle might be just 10%, this makes a massive difference to the input ripple and the amount of input filtering needed. In actual testing, Murata measured at least 40% improvement with no input capacitance comparing with an equivalent single-stage buck regulator with some input capacitance as shown here.