By late wotlk they actually ended up getting rid of it's traveling time, and then in cata it was troll when they added the interrupt portion to it's effect because the silence had no travel time but the lockout did so you would pmuch never lock anyone out with silencing shot lol
Do you have any source of this? I mean I remember it as always having a travel time tho it was very fast by the end of Wotlk. I even asked my friend who's main MM I played together alot in Wotlk and he comfirmed it too. As I recall the only change to Silencing shot during Wotlk was removing it from GCD and adding interrupt to non-player targets.