The full quote in context was: "You can name a thousand great instrumentalists or you can name a thousand great vocalists, but he’s the only person you could find who changed the way people played their instruments and the way people sang. Louis does that in a four-year period in the 1920s; by 1930, if you aren’t playing or singing like him, you’re out of work."

You forgot (or missed) the rest of the quote:

> …and the way people sang.

As the article stated, many great artists changed one or the other, but only Louis did both.

That's not how I interpreted it, but it's a fair point.

I think it's pretty clear in context.

More importantly though, Armstrong's influence on instrumentals alone was far broader than Hendrix (who mostly affected how electric guitars were approached in pop music, and a little bit beyond) Hendrix is a giant, absolutely, but not in the same league.