i suspect that the details haven't been discussed because there isn't really a concrete plan out there. although one thing that was clarified in reading an article about this is that "younger workers" means under 55.
speculating with a friend, we came to this conclusion: it probably saves money because, in the end, you end up trading a fixed chunk of money (which you invest) for a percentage of what you'd get monthly when you retire. and with people now living longer, survivor benefits, etc. the first is a whole lot less than the second. hence the short term "hole" while those 55+ continue to collect.
dunno. in those terms, it doesn't sound like a good deal. as a "safety net", i mean. if you're gonna give me something to invest, give it to me outright so it can put it in gold, say.
but i suspect the motives are different. (apparently all three plans that the previous bipartisan commission came up with involved these accounts.) my guess is that they're really there to address what happens when boomers (1) stop contributing to their iras and 401k's after retirement and (2) start withdrawing. (similarly, big pension funds like calpers.) less about "wealth creation" and more about "preventing an implosion".