This is specifically not supposed to work. During development of the unique the stat description was set to make this clear, saying "...when you gain a Buff from your Aspect of the Avian Skill". But it looks like that was changed to the current wording at some later time when cleaning up the descriptions. My best guess is the clearer one was word-wrapping on some resolutions, and was changed to be shorter without realising that the part specifying it had to be your aspect of the avian skill was important. I have made a note to get this improved in the future.
Thanks for pointing it out.