Velcro only has a plastic backing when it is intended to stick on. This is the kind most robotics folks are more familiar with. Most Velcro doesn't, though, because it is intended to be sewn on.
Ropes made of plastic are pretty common. I'm pretty sure one of the ropes in the picture in the game manual could be plastic even.
I will be interested to see how they clarify this in the Q&A. They may outlaw Velcro, but I think they will have to add language to the rule to do so.