[KenWittlief]

I think its risky to read things into the rules that are not there. In this case Im not talking about the difficultys of technical writing.

Extend means extend. If I say I can extend my head so I am 8 feet tall, then I stand on a ladder, you will laugh at me.

If FIRST means that no robot shall break the horizontal plane X feet above the floor for any reason, then they would have said that.

If you are not allowed to extend, that does not mean you cannot jump, hop, float, fly, toss a ball in the air, send up a blast of air.... or climb

adding (what is not there) to the rules will limit the creativity of the teams coming up with unique ideas.