I think it just depends on how similar the card you have is to the card whose BIOS you're flashing.
For example, if you card has two fans and you flash with BIOS from a card that has only one fan, you might only see one of your fans working. In the case of your audio not working, my best guess would be that perhaps the ports are laid out physically differently or just addressed differently in the BIOS, something like that.
But that's all speculation on my part, I don't know much of anything about this. The only way I could try to figure out more as a lay person would be to try another 1080 Ti's BIOS and see what happens. If you were comfortable doing that.