NEWS, bash-5.1, item 1.o. says: o. Bash posix mode now treats assignment statements preceding shell function definitions the same as in its default mode, since POSIX has changed and no longer requires those assignments to persist after the function returns (POSIX interp 654).
This refers to the following POSIX change, I guess: https://www.austingroupbugs.net/view.php?id=654 IMHO the wording "preceding shell function definitions" is misleading, because the assignment precedes the function call, not its definition.
