You cannot make curves with a lot of samples stiff (or at least i don't know how to). But as soon as you have less points it starts to react the way you expect. This workaround is not ideal for characters with hair that needs the resolution.
Let me know what you guys think could be the solution here
also in a side note, 1 billion stiffness on default and 0.1 bend stiffness on default is very confusing to a core user who has no grains experience.