This bug is NSViewAnimation documentation lists effect values among animation-option keys. It was filed on 2006-04-14 at 23:15 PDT.
The Constants section of the NSViewAnimation reference lists the two effect values among the animation-option keys.
Steps to Reproduce:
The effect values, NSViewAnimationFadeInEffect and NSViewAnimationFadeOutEffect, have a separate table from the option keys (such as NSViewAnimationEffectKey, the key for which the two *Effect constants are legal values).
NSViewAnimationFadeInEffect and NSViewAnimationFadeOutEffect are listed in the same table with the option keys.