Okay, first off, my comments are being made not having RTFA.
But there seems to be a difference here. First off, did TBS grant (and by "grant" I mean "sell") approval to MXC or Ninja Warrior? 'Cuz if they did I can see them turning a blind eye.
It also seems to me that those two shows are more "derivative works" of their Japanese counterparts than anything, whereas Wipeout is theft-of-concept, if indeed the concept of "making snarky-and-only-marginally-funny comments while people run an impossible obstacle course" is copyrightable.