Ok, I understand now.
The in-game sensitivity calculation is intended for those who do not mess around in the config files at all, so it is locked to the default multiplier.
What I can possibly do is to make a switch for the config file sensitivity where you select if you want to calculate the sensitivity or multiplier (like the option already available for ADS). Or perhaps a similar option for the config file.
I need to see how this interacts with all other calculations though, but I'll take a look at it.