The lexicon is checkable: Kyoka Suigetsu, the idiom for the unattainable image; Zangetsu, slaying moon; Senbonzakura, a thousand cherry trees; Hyorinmaru, ice ring; Suzumushi, the bell cricket, an insect famous for its song, matched to a blind swordsman's sound-based blade; Benihime, crimson princess. And the naming is mechanical, not decorative: a Soul Reaper must learn the sword's true name to release it at all, and bargain with its spirit to master it. The power system is philology.
The folk layer literalizes it: fans always treated zanpakuto spirits as people, and the anime's Zanpakuto Unknown Tales arc eventually drew them as a full cast, the spirits walking, sulking, rebelling. The relationship is framed in-story as marriage, apprenticeship, or hostage negotiation depending on the wielder.
The reader's revenge theory: Kubo foreshadows by nomenclature, so the fandom learned to read every new name as a leak. Kyoka Suigetsu was the proof of concept, and after it, readers parsed each captain's blade as a character reference, finding the pattern more often than chance should allow. The claim in its strongest form: nothing in Bleach is named innocently, and the name is always the first page of the twist.
Kubo named the traitor's sword Illusion in chapter one and nobody read the dictionary. What else in the series is a spoiler hidden in the glossary?