The mistake is to use "canon" to mean "real and binding." The canon, however coherent or inclusive it may be, is still just a big elaborate story people told, so no part of it is any more "real" than a ghost story told around a campfire. It was invented, and so it can be reinvented, reinterpreted, retconned, or ignored.
Any idea from a series canon may be useful
for later storytellers to draw on if they so desire -- or it may be useful for them to ignore or contradict if that suits their needs better. But worrying about whether it's "real" is kind of pointless. It's part of the story, but stories can be adjusted and revised in ways that reality can't.