According to Mavke (I think is the developer of Nibitor), the only things that the card recognize is the VID number between 1 to 4. 4 = 1.1V, 3 = 1.05V, ...
When you see in nibitor 1.1V, this only a label that nibitor make correspond to a VID but this label is only internal to nibitor and it's not taken from the bios.
So it is not possible to go higher than 1.1V since the card doesn't recognize other VID. This has been confirmed by Jason who tried to set the VID to 5, but as result the card reverted to a lower value, probably 1.05V.
Some people also tried to change the label in nibitor but as explained later by mavke, it didn't do nothing. It was also confirmed by the multimeter.
So I'm not sure what hex value you are reading but it is not the Vcore value. All the explanation above can be found in the previous posts. Check for Makve's one.
And as you can see in the image below, the part of the bios you are reading doesn't seem to be a part of the voltage table:
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