I remember interviewing for a job 20 years ago at an insurance company where they explicitly listed "must have experience with the XYZ123ABC system" where that was just a name they gave to one of their internal systems; no one outside of that company would have ever come across it. I tried explaining to the recruiter that unless they were limiting the position to internal applicants, they should ask for experience with whatever tech was used to build the system rather than the system itself. She was completely baffled by that.
That does sometimes intentionally happen if the company has a specific visa candidate or internal employee selected for the position but is required to post a public facing position - that's also where you'll see extremely specific and unrelated tech requirements like "15 years web development, 5 years embedded system driver development, maintainer of at least two major open source projects".
