Yeah, I saw that announcement but still can't figure out what the actual impact is - doesn't change anything for me (my non-skill slash commands still work).

The actual impact is that there should be less confusion in the future about "what's the difference between these two" because there isn't really.

To overly programmer-brain it, a slash command is just a skill with a null frontmatter. This means that it doesn't participate in progressive disclosure, aka Claude won't consider invoking it automatically.