Sharpening Vs. Vignette in Aperture

One more item to tuck away in the Aperture corner of your mind...

Observed an odd behavior on Aperture 3.4.2 yesterday evening. After applying sharpening to a photo, I added a post-crop vignette. The vignette "altered" the sharpening in some areas of the photo. Quickly dealt with by brushing away the vignette from the impacted areas.

I don't quite know how better to describe this, so I captured what I experienced in a short video.