Locks don't matter. If a pursuer walks into your smoke bomb, you'll be able to stun them, assuming you're quick enough.
Some things to remember though are that smoke bombs don't work right away, there's about 1/3 of a second in between dropping them and seeing the effect. So pursuers sometimes appear to kill you right through the smoke. (You should sometimes see a message about this after you die, if it's happening continually.)
And also, a pursuer can stand at the edge of a smoke bomb and kill a target within the smoke if the target is close enough. To counter this, stand right in the middle, or keep the smoke between you and your pursuer until they start coughing. Most people catch the edge when trying to get round a smoke bomb. The effect seems to be slightly wider than it appears on the screen.
Lastly, take a little step back after dropping a smoke bomb at your feet. The smoke doesn't always appear all around you, sometimes your character drops it to the side and ends up only just standing in the smoke. Or other times impatience gets the best of people and they try to run forward for the stun right after dropping the smoke, only to bump straight into an uneffected pursuer's blade. Taking a small step away from your pursuer/target in this situation oftens encourages them to come forward, right into your smoke, or out of their own, as the case may be.