Thread is getting a little long, opening a new one.
Previous thread: http://elderscrolls.wikia.com/wiki/Thread:308536
I proved IN-GAME that this urn only apperas IF AND ONLY IF THE PLAYER KILLS SAADIA. This urn doesn't appear if you hand her ovet to Kematu as I proved in 3 playthroughs.
Actually Saadia's Urn appears in Whiterun's Catacombs if she gets killed. It doesn't have to be the Player. But yes, I can confirm as well that if you hand Saadia over to the Alik'r Warriors, her Urn will not appear.
I have a pretty far-fetched theory that Kematu and Saadia had nothing to do with the Thalmor. They only accuse each other of being Traitors to appeal to the Dragonborn as the Redguards are often shown to be more cunning than the Nords and willing to resort to trickery and lies to get what they want.
I suspect this is just a Hammerfell's own internal political strife between the Crowns and Forebears. They have been fighting for centuries, even if most of the Crowns and Forebears had reconciled with each other, I believe there'll be a minority who kept fighting against each other in the shadows.