Here is the proposal itself, from Assembly Member Bass, after a few changes made in mid-April. As you'll see when you read it, the main change is moving the sentencing intentions and definitions out of the proposal itself, as well as out of the hands of the legislature, and into the hands of the commission, whose purpose is now defined much more vaguely:
There is hereby established an independent, multijurisdictional body to provide a nonpartisan forum of statewide policy development, information development, research, and planning concerning criminal sentences and their effects.
This is much vaguer than the original intent behind the proposition, and may have to do with the ability to better "sell" a body whose authority is not clearly defined, as well as with the will to keep the commission free from constraints. It also might mean that their decisions would not necessarily be binding. Who knows? Interestingly, Crime Victims United of California consider A.B. 1376 a "placeholder" bill, and see it as a cause for concern.