You are probably encountering a bug in Unreal Engine 4, where some games read a generic UE4 file and applies some settings from it.
Check if you have a file called UserInput.ini under the folder %LOCALAPPDATA%\Unreal Engine\Engine\Config.
If you do, try to delete it and see if it changes the sensitivity behavior for both PUBG and Kovaak's.
PS, you should always enter the configured FOV and not the scope/ADS FOV. The scope FOV/ADS will be either calculated based on the config FOV, or locked to a specific value. In this case it doesn't matter since the ADS FOV in PUBG is locked, but as a general rule always enter the config FOV