To sum up: ex-Yahoo employees want this story to be about the technical recklessness of the request and Yahoo’s bureaucratic implementation of it. Government lawyers and spooks are happy to explain this was a traditional FISA order, but want to downplay the intrusiveness and recklessness of this by claiming it just involved adapting an existing scan. And intelligence committee members mistakenly believed this scan happened under Section 702, and wanted to make it a 702 renewal fight issue, but since appear to have learned differently.
This is the definitive summarization of what Yahoo! (likely) did when they monitored all of their customers’ emails for the US government. Well worth the read for its content and, also, to see what goes into a critical media evaluation of an unfolding intelligence-related series of news stories.