in i18npool/source/breakiterator/breakiteratorImpl.cxx

we have in case WordType::WORD_COUNT:

while (nPos > 0 && (u_isUWhiteSpace(ch = Text.iterateCodePoints(&pos, -1))) ||
isZWSP(ch)) nPos=pos;

operator precedence of && before || gives this the meaning of

while ((nPos > 0 && (u_isUWhiteSpace(ch = Text.iterateCodePoints(&pos, -1)))) ||
isZWSP(ch)) nPos=pos;

(as attachment one does to make it explicit)

but looking at the *other* case statements that looks a little suspicious, the
other similar ones do...

while (nPos > 0 && (u_isWhitespace(ch = Text.iterateCodePoints(&pos, -1)) ||
isZWSP(ch))) nPos=pos;

so the intent *might* have been as in attachment 2 [details] to make the logic equivalent
to the other types