I wonder the same thing. When I saw the tethers in the competition, I was like "What the heck!?!?" because from my interpretation of the rules they were totally not allowed. In our design faze, we scratched out the idea totally because of there rule. I see the refs are calling a lot of stuff and DQ'ing a lot this season for numerous reasons. I saw a match at Lone Star that I thought surely would have been intanglement but it wasn't. This is seriously angering me because it is not being called at all yet we were really getting DQ threats from the head judge about the way we lifted the goal from the flanges.(our mechanism frequently slipped off the flanges and reacted against the wood). Now I think if they are going to call that, they should call some entanglement.
We asked the judge about that and she said it depends on what the refs call entanglement, she was very friendly about it though I was not satisfied with the response.