Block Level Power Pins

[kareefardi]

This question surfaced when looking at some of the test cases in pdn that are using upf. I got confused as to how exactly OpenROAD decides to use a specific power net as a block level power pin. For example, power_switch_upf_regions.tcl doesn't declare block level power pins at all. Also, power_switch_upf_star.tcl declares the output from the power switch cell as block level but doesn't do the same for the input to the power switch cell.
I noticed the argument -pins in define_pdn_grid, this will select nets based on layers but will not filter out certain nets. At the moment, I don't think this is a problem but I am still wondering about how the tool operates.