People need to understand the game more... SOMBRA CAN NOT CANCEL A TRANSFORMATION ULTIMATE.. (Soldier, Genji, Mercy, Torb etc) once the ult is activated the only way to stop transformations is to kill them. He also activated right before the hack completed as well
Please read sombra hack ability details. Just google it and you’ll see how long it takes for the hack to finish and after that how long it takes for it to take effect. It’s not instant. It will also explain which abilities are effected by it and which are not.