According to the paper, the leak occurs when the battery is close to full (>95%). In that case, since the battery is almost full, the power drained from the charger reflects the concurrent power being consumed by the device.

I initially thought this is easily fixable (for example, by always request full power), but then I realized it isn't, since the extra power would then have to be dissipated as heat, which is a bad cellphone UX as well.