People running on reaction to teleslash is not a 'myth'. It's possible and the fact that you say otherwise proves that you only play against people who don't know the matchup/lack experience against Kenshi.
Of course you don't spam teleflurry, they'll just start ducking it and punish you from full screen. That's Kenshi's biggest flaw, his MAIN zoning tool is so unsafe, using it is a big risk, and unfortunately the risk/reward is not in his favor.