Understanding Power Good Signal in TPS54719
As the powergood output is an open drain, it can only pull low, or do nothing, so that is why it needs another device like a resistor to pull up.
Because the enable input already has an internal pull-up current source, no external resistor is needed.
And because VOUT is settable by user with external output voltage setting resistors, it is the voltage-divided feedback sent to VSENSE pin which is compared to internal tresholds. This way it works regardless of how the user has selected the VOUT, because Vout basically sets the VSENSE pin voltage via the feedback resistors.