artngoodfeelings Sorry for the confusion. The default curve is used when it can't be determined from the surrounding keys which curve to use, which is what the description says affects. For example, if you add a new key for a bone during animation when there is no key for that bone yet.
From your screenshot, it looks like you always want to use the Bézier curve, so you might want to enable the Automatic
button. When enabled, the handles are set to automatic and the angle of the handles is adjusted automatically based on the values of the keys before and after the key. If the handles are moved manually, they are changed back to manual handles.