Pretty sure this is my last comment, because what you just quoted about soundness is, in fact, a direct consequence of Löb’s Theorem. For any proposition P, Löb’s Theorem says that □(□P→P)→□P. Let P be a statement already disproven, e.g. “2+2=5”. This means we already had □¬P, and now we have □(¬P & P), which is what inconsistency means. Again, it seemed like you understood this earlier.
Pretty sure this is my last comment, because what you just quoted about soundness is, in fact, a direct consequence of Löb’s Theorem. For any proposition P, Löb’s Theorem says that □(□P→P)→□P. Let P be a statement already disproven, e.g. “2+2=5”. This means we already had □¬P, and now we have □(¬P & P), which is what inconsistency means. Again, it seemed like you understood this earlier.