'Transparency', i.e. sharing proprietary data, is a big part of being regulated. From the rejection notice:

"First, the exchange must have surveillance-sharing agreements with significant markets for trading the underlying commodity or derivatives on that commodity. And second, those markets must be regulated."

Then in the footnote:

"the significant markets relating to the commodity-trust ETPs approved to date have been well-established regulated futures markets for the underlying commodity"

It looks to me like this could be the hurdle.