The UU memorandum of understanding is irrelevant. I am not a member, and I think most atheists are not either. People should not be required to join a church or a religion to join the scouts.
I don’t believe in any gods, and would never say that something was a god if I did not think it was a god. Consciousness is not a god, nature is not a god, the laws of thermodynamics are not gods. Labeling these things gods only serves to imply some sort of mystery thing about it when there is none, I would consider it lying to do so. Do you think they would accept me? I don’t.
If the religious aspects were truly left to the scouts and their families, outright atheists would simply be accepted, and there would not need to be a memorandum of understanding so that a specific organization could participate, because they would have simply been accept beforehand.