This is the most amusing part of the article:
"The reason that Apple includes such an old version of Bash in its operating system has to do with licensing. Since version 4.0 (successor of 3.2), Bash uses the GNU General Public License v3 (GPLv3), which Apple does not (want to) support. You can find some discussions about this here and here. Version 3.2 of GNU Bash is the last version with GPLv2, which Apple accepts, and so it sticks with it.
"This means that the entire world (e.g. Linux) proceeds with new versions of Bash, whereas macOS users are stuck with an old version from a decade ago."
Problem with script functionality on Ubuntu Linux and MacOS (all 6)