NSA also pays the owner of the Washington Post upwards of $10 billion for cloud services

That's not the only publication that had access to the documents. From wikipedia

>the first of Snowden's documents were published simultaneously by The Washington Post and The Guardian. [...] The disclosure continued throughout 2013, and a small portion of the estimated full cache of documents was later published by other media outlets worldwide, most notably The New York Times (United States), the Canadian Broadcasting Corporation, the Australian Broadcasting Corporation, Der Spiegel (Germany), O Globo (Brazil), Le Monde (France), L'espresso (Italy), NRC Handelsblad (the Netherlands), Dagbladet (Norway), El País (Spain), and Sveriges Television (Sweden).

Wouldn't be more likely that a plant would actually not say that, but rather come up with something else? Seems much more likely that a plant would promote some other aspect of a leak that would be less damaging as the story. Or even possibly making part of the document dump disappear.