My optimistic side says the sudden negative buzz is a plant, because they're so confident it's good that they want people to say, "Holy s***, it's actually awesome!"
Mostly it just seems like BS falling from the sky out of nowhere. Suddenly a guy who knows a guy says something totally contrary to all other available information (that production was tense and difficult), and that it's not actually very good? Uh, what? OK, I heard you. But it means very little to me.
I feel similarly about the good review. It's not really "over the top" in my opinion. It says the cast is good, Spalko is memorable, Ford does a great job and brings poignancy...it's not declaring an instant Oscar winner or anything. Just optimism. But it, too has come out of nowhere.
Maybe they're *both* plants? Those two things appearing more or less simultaneously create a lot of tension around places like this. The negative and positive kind of combine to create a powerful "über buzz."