1) Yes, it is sourced. It comes from NowCasting.com, which doesn't operate on user submissions. The casting sides on that site are directly from the production studios. It's proved infinitely reliable for countless other shows. People have been sourcing it from the beginning.
2) Uh huh. They do. We can operate under the assumption they just might go ahead and do that. But as of the release of those sides, the information is completely reliable, and thus wonderful fodder for spoiler speculation all across this internet of ours.