Let's just test it on a release, I've picked http://musicbrainz.org/release/4ac84de9-8726-49d2-b01e-924d4905dde0 .

Edit release, go to tracklist tab, click on "credits". There is no tooltip present for Beyoncé (screenshot 1). The tooltip for other artists on this release is okay (screenshot 2). The tooltip is there even if you'll change the artist into another one. It's only missing for Beyoncé.