While I don't know all that much about Oteil, I'm willing to bet he doesn't understand the laws of physics better than the average bass player. Incresing the non vibrating part of the string will have no effect on tension. It's the law, no matter what Fodera or Oteil say.
It might have effect on the feel of the string, but I'd say it may actually make the string feel looser. I haven't seen any experiments done on basses, but I have seen experiments (I believe it was posted in the MIMF archive) where identical archtop guitars were built, except for the length of the non vibrating part of the string. In this experiment, the longer string felt looser, which is the opposite of what most bass players are looking for. There may be other variables on archtops that aren't on electric basses, but that was the only real study I've seen.
But is there REALLY a difference, or do Oteil and other just think there is? Fodera has a lot of psychological advatanges to make people think they feel a difference even if there really is none. They're a well respected company, why would they try to fool us? They make some of the best basses in the world, which sell for top dollar, there must be something different that makes them better. It's a no cost option, so they're not making any extra money off it. All these things are little psychological traps we all fall into, which make us believe them even if they're wrong. Our brain likes things to make sence and to people who don't understand the physics behind it, it doesn't make sence that an extended headstock would feel the same as a traditional headstock, so our brain tricks us into thinking it's better.