Yes, I've seen the same thing with a user who saved a preset with a colon in the name. That too will fail. What actually happens is that a file is created with just the part in front of the slash as name, and no file extension. Don't use (illegal) characters that you wouldn't use in a file name either (because presets must be saved as files).
That's really strange undocumented behavior. The name should never be directly used as a filename, there should be a difference between the filename and the formatted name string. What if I want to use diacritics in the name? In German those are very common, but having a diacritic in a filename can lead to all sorts of bugs depending on the OS. Also, it wouldn't be hard at all to rewrite those unsupported characters to a generic placeholder such as an underscore and still use the name the user wrote for the actual name of the preset, which seems to be contained in the XMP file. I confirmed that the name shows up correctly when I change it in the XMP after I created the preset:
<rdf:li xml:lang="x-default">Modern _ Warm</rdf:li>
After changing this, the name shows up correctly in the Program. So it's really an arbitrary restriction that shouldn't exist. And again, even if it can't or won't be fixed, there should at least be some sort of error message or warning regarding the invalid name.
It’s a bug, and I have already reported it.