I don't recall that many shooters giving an option. I personally always hated non-toggle. Don't get how people can aim with one button pressed.
every shooter i have played i have been able to hold right mouse button to aim down sights without it being a toggle, which is why i just cant get used to the toggle way, nor do i want to get use to toggle.
i dont mean this in a rude way, but just because you dont get how people can aim with one button pressed, doesnt mean the same for others. im sure if this game didnt have the option to be a toggle, and was press to hold only, you would be frustrated also.
i am using the "fix" that can be edited in the ini file, but it is buggy and results in alot of deaths and frustration.