According to the data sheet "8.4.2 Pass Through (VIN > VOUT)", when VIN > VOUT state, switching of High & Low side MOSFET stops, Vf of Body diode of High side MOSFET from VIN and inductor A value that is obtained by subtracting the voltage dropped by the DCR of the voltage appears on the VOUT side.

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* This answer is for the manual at the time of Rev.D.
Please note that chapters and drawing numbers may change when the datasheet is updated to a new revision.