It is not recommended to connect the resistor to the Vcc pin from the HV.
Looking at the datasheet we can see the following notes on page 17.
The LM5021 is designed for ultra-low start-up current into the VIN pin. To achieve this very low start-up current,
the VCC regulator of the LM5021 is unique as compared to the VCC regulator used in other controllers of the
LM5xxx family. The LM5021 is designed specifically for applications with the bias winding connected to the VIN
pin as shown in Figure 13.
NOTE
It is not recommended that the bias winding be connected to the VCC pin of the LM5021.
Doing so can cause the device to operate incorrectly or not at all.
Connecting the bias winding or a resistor to the Vcc pin increases the risk of injecting noise into the internal circuits in the IC that are powered from the Vcc rail.
TI cannot recommend the addition of this resistor to decrease the start-up voltage as this may cause the controller to malfunction if there is voltage transients or noise on the HV supply..
