That's true, sort of. Whatever the approvals process is, it isn't free. I imagine 99% of the indies will not get much support, if any, from Sony or MS in terms of marketing etc. Maybe the cream of the crop will get some attention, but probably not for free. I'm not sure how that works in the various smartphone stores.
As the provider of the digital marketplace MS and Sony will provide marketing. Look at what Apple does with its app store. Popularity list, editor picks, genius are all forms of marketing that apps depend on. Apple provides quality control, marketing and distribution, MS and Sony will do the same. Thats basically the function of a publisher.