There are two time periods where a Boost converter, even under no load, can have high input current levels.
The first time period is before the Boost converter even starts to switch which is referred to as inrush, as there is a path from the input to output through the inductor and diode. The current during this period is only limited by the impedances in the circuit.
The second period is when the output capacitors are charged from 0V (or VIN, see above) up to the target output voltage. The current during this period is limited by either the Soft Start function, or the current sense resistor hitting its upper threshold. These design values would be determined by the maximum output current, and by conservation of energy the peak input current is always higher than the designed maximum output current for a Boost converter.