I guess this is for shell scripts that need to work with "unsafe" filenames?
I've been using Linux since 1999 and i never came across a filename with newlines. On the other hand, pretty much all "ls parsing" i've done was on the command-line to pipe it to other stuff in files i was 100.1% sure would be fine.
When teaching beginners shell, it's natural to teach `ls` for listing directory contents. It's also natural to extend from `ls` to `ls | ...` for processing lists of files
The important point to get across is that pipes let us build bigger commands from the commands we already know. If needed, you can back up later to teach patterns like `find [...] -exec`, `find [...] -print0 | xargs -0 [...]`, `find [...] | while read -r file; do [...] done` and so on.
There are all kinds of prerequisites to creating files with unusual names. Those barriers tend to mean beginners won't run into file name processing edge cases for a while. The exception will be files they download from the Internet. But the complexity there will usually be quote and non-ASCII Unicode characters, not newlines or other control codes.
In teaching, the one filename complexity I would try to get ahead of, preventively, is spaces. There was a time, way back when, when newbies seemed to expect to stick with short, simple filenames. These days they the people I've helped tended to be used to using spaces in file names in Finder and Explorer for office or school work.
I've been using Linux since 1999 and i never came across a filename with newlines. On the other hand, pretty much all "ls parsing" i've done was on the command-line to pipe it to other stuff in files i was 100.1% sure would be fine.