"Breaking change" is a pretty common term, especially here, so I don't get the confusion about what it means. It means an interface-breaking change, so that the same input produces a different output, and is generally to be avoided because it forces the user to have to adapt and means the new version isn't strictly better[1].

The inclusion of autocorrect (that I mentioned) would be example here: previously, it would accept whatever text you gave it verbatim. Now, it will sometimes change non-dictionary strings to dictionary words.

(Another thing that bothered me was that, on the update, it forgot my font settings and I had to work to re-find them.)

I'm happy to admit my phrasing was confusing, but not enough so that you would be unable to see the relevant failure mode.

[1] https://stackoverflow.com/a/21703427