I don’t know what the plugin does but script to append an audio file to all audio files is possible to do cleanly in just three lines. Being able to write three lines doesn’t make something good at programming, and taking many more lines would make it bad at programming.

Many senior level “software engineers” are just tenured programmers and they’re managed by business people who don’t know software engineering either. One of the major benefits of using off the shelf software libraries is that they generally work as expected and have been through much more testing than something you just wrote, and often these libraries even receive free or cheap maintenance updates. You don’t want your developers wasting time reimplementing things and then wasting more time maintaining those reimplementations.

Getting the AI to write it is like mitigating the initial reimplementation cost by going to Fiver.