On Overcoming Bias Hanson asks what is verifiable.

One comment includes: Play the "double crux game", where any disagreement regarding something unverifiable is reduced to an assertion which is simpler to check, which is reduced to an assertion that is simpler to check, which is eventually reduced to an assertion that all agree is verifiable.

While I think the idea of double crux is very useful in identifying sources of disagreement that allow people to avoid talking past one another I question the idea that it would necessarily lead to allowing some higher level claim be verified.

It strikes me as something of a fallacy of composition type error.

Does this seem a reasonable view to others?