They were non-traversable. The worm-hole theories were mathematical descriptions that outline that wormholes could exist. The study of Quantum Entanglement is the most recent advancement on his original theories that I am aware of.

They have gotten hung up on things. One hangup is with causality, and that its still a fundamental belief that effect shall never proceed before its cause. The other hangup is with the Principle of locality and the fundamental belief that an object can only be affected by its immediate surroundings.

So the only thing that really ties it all together are their hidden-variable theories. So, they were crazy about quantification, and found ways to make the theories adaptive to one another the best they could.