Yes the origin of the UID approach was in the card-based manual system where the zettlekasten creator used a complex code to connect individual cards. That alphanumeric code tracked how he believed the notes related and developed. When the technique moved to digital collation systems the complex branching code was dropped but it was often necessary to have one unique id per note in order to link to notes. Now with bidirectional linking there is no need for that - UNLESS you want to be sure that you can export and index in a different tool. Seems like an enormous amount of effort to me personally when you have the functionality now being built into tools like Obsidian or Roam.
In my humble opinion what many users are missing about Zettlekasten is that the value is in the process of stopping and thinking how your notes connect. There is much excitement about new digital tools that allow you to link on the fly but that risk falling right back into the Collectors Fallacy that the Zettlekasten system values was in avoiding. The belief seems to be that the digital tool will do all the connecting for you - and there is value in serendipitous discovery. But the value of Zettlekasten is rooted a great deal in the fact it forces you to think about your notes and how they connect and how they ought to be organized.