The changes are absolutely final. They finish most of the contents of the patch months in advance and put it through rounds of testing by over 100 QA staff, who wittle down the number of bugs from several thousand to a small number (listed at the bottom of the notes as "Known Issues"). They then put it through a final QA I believe, about 2 weeks prior to release, so they can't make any changes during that time. In other words, by the time we saw the BLM changes, it was aleady too late for them to change it.

The prelim notes do not include some things occasionally, such as job reworks, known issues, lists of specific items added, etc.

The reason for the Black Mage changes will most definitely have to be on this page after the final notes release: https://na.finalfantasyxiv.com/jobguide/battle#battleaction