Most stemming use cases are trivially solved with a regex. That's the point he was making. The difference between a beginner and expert with regexes is quite a lot.
Maybe! Full-text search is great for text. Command lines have some things in common with text, but they definitely aren't normal text. E.g., punctuation is much more significant. Stemming may not be appropriate. Case matters. Word boundaries are different, and many of the significant lumps aren't really words.