Well, you did pretty much say that it "stinks" of superstition, and you asked rhetorically if it was okay for a coach to make decisions based on superstition.
I think the Jets feel that Niku's development needs a bit more work, and maybe a bit of a reality check that he still needs to be more focused on defense when he doesn't have the puck. I'm the first to be after Maurice for playing Sbisa, Bitetto and even Beaulieu, and his previous penchant for playing vets. But I don't think the decision vis-a-vis Niku is based on "superstition". It might have been to keep a winning line-up together. It might even have been to help the Jets save a bit of cash. But I think it was also to get Niku playing at a level that would keep him in the NHL long term. That meant getting him healthy, in shape, and playing consistently defensively. Imagine the scenario where you bring in Niku and replace another D in a winning line-up and they start losing and Niku is struggling defensively. That would be a worst case scenario for Niku's development and positioning with the team.