It helps to RTFM some times: (https://www.gnu.org/software/gettext/manual/html_node/PO-Files.html)

This flag can be generated by the msgmerge program or it can be inserted by the translator herself. It shows that the msgstr string might not be a correct translation (anymore). Only the translator can judge if the translation requires further modification, or is acceptable as is. Once satisfied with the translation, she then removes this fuzzy attribute. The msgmerge program inserts this when it combined the msgid and msgstr entries after fuzzy search only.

Fuzzy is only a mark for things gettext thinks have changed and the translation may not be 100% correct any more. It does not keep that string from being used.