All the inputs to report_power tool are saved in the XDC constraints of the project and will be populated if report_power tool is invoked again in the flow. This is useful for the what-if analysis. The most recent switching activity constraints are retained and appear in the tool. Even if you provide inputs through XDC based commands in Tcl console of Vivado® Integrated Design Environment or through the Net Properties window (Edit Properties in Power tab), these input values will reflect in report_power tool. XDC constraints for switching activity will be in sync with the report_power tool. Any change made in the tool will reflect in the XDC constraints and vice-versa.
This is also helpful, if you want to override the default switching activity in the report_power tool. In this case, you can create XDC constraints with desired default values and run report_power.