Fyi, my wild Bold Corsola (lol) failed the applet because its nature was Synchronized. However, Synchronized legendaries appear to be included in the applet, though. So, the testing should be helpful. ^^
Shoddy's Team Builder checks IVs the same way.
I just tossed the shiny Latias because fleeing legendary Pokemon cannot be Synchronized and besides, she would have awful IVs (this is a Gen III glitch - beasts have awful IVs too).
She was palparked at level 40, so she is obviously not from Southern Island, so she is a runner. ^^