The option bytes are wrongly set when using big flash derivative STM32G0B1RC and STM32CubeProgrammer 2.13 (it doesn't matter if CLI or GUI).
The point is that the protection is set for the second bank.
Documented on pictures, the state of OB in MCU before flashing hex file (containing OB) - 2023-05-09_09_35_57.png,
and the state of OB after programming is done - 2023-05-09_09_39_46.png.
Also, attached output from CLI after OB was wrongly programmed, and protection was set, we couldn't do mass erase - 2023-05-09_09_40_16u.png.
I noticed the document https://www.st.com/content/ccc/resource/technical/document/release_note/group0/0e/66/57/b4/f9/ee/4f/73/DM00441049/files/DM00441049.pdf/jcr:content/translations/en.DM00441049.pdf in which is described fix for STM32G0Bx in version 2.13.1, but I cannot find this version for Windows OS.
Can you look at this issue and reproduce it?
For now, we have a workaround - omit OBs from the hex file.
