It depends on what you use it to do. I occasionally extend my lead arm to cover my chin as a form of defense, which works well. I prefer to fight on the outside and nobody can really get in on me if I put my glove in their face (it's best to do this while resetting your range, to keep them from compromising it by following you). Also, just pushing on their gloves/chest/head works, but it's risky if you don't have a long frame.. which obviously doesn't apply to Jones.
But, it's not really advisable to do the "open hand technique" with your lead hand, simply for the reason that doing so with your rear hand provides a more accurate means of finding range (because if you aren't close enough to touch them with your right hand, how are you gonna land your more forward left hand?) and also preserves your faster lead handed counters. When Jones extends his lead hand he completely removes his ability to counterjab or throw left hooks; it only works for him because nobody can really get close to him once his hand is in your face, and also because he doesn't give a shit if you run onto his fingers.