I think it's as simple as a misinterpretation of the technical intel-community jargon being used by NSA.

They're saying PRISM gets them access to Google/Facebook/etc.'s data with no other middleman. That's not always the case; when working with international partners NSA might obtain intel from other (foreign) intelligence agencies, or their HUMINT might report data that is itself hearsay.

So the source/provenance of data is very important for an intelligence agency. NSA is saying this (with PRISM) is the best case as far as the source of intel goes, there is no better primary source.

That still doesn't mean NSA has embedded backdoors or that the company doesn't control access to the data though. Data Access is a separate concept from Data Source in intel.

We can still say that having this kind of access to data is above the capabilities NSA needs to have (it certainly seems ripe for abuse) but it's sounding like the reality is not quite as sinister as Greenwald or WaPo had been led to believe.