Surely the examples you provide are simply revelations in an ongoing story. Or else every piece of information revealed from before the plot's present is a retcon. Assumptions can be challenged by surprising plot twists that is simply narrative progression, no?
Yes, that's the point. It's called retroactive continuity, not retroactive contradiction. It's supposed to be consistent, even though it wasn't revealed until later. At most, it contradicts our assumptions, but it can simply be something added later that's treated like it was true all along.
I would argue the only real definition of a retcon would be an alteration to pre-established facts.
That's what people believe these days, but my whole point is that that's a misunderstanding of the original meaning of the term. It's like using "literally" to mean "figuratively," or using "decimate" to mean "destroy almost entirely" instead of "destroy only 10 percent of." It's a pervasive usage, but it's a change from the original meaning.