But…Jimmy Jam and Terry Lewis are artists lol. They were in The Time and wrote some songs with Prince and Morris Day. Physical Graffiti was basically their album idea and Prince came in and said “ok this is mine now.”
I think you’re trying to say Chad and others who play instruments but (allegedly) don’t write songs are session musicians instead of artists. I don’t believe that to be the case. Certainly not for people who contribute to the creative process and help craft/write songs. If you want to say Pharrell was the more prolific writer I’d agree with you, But they’re both artists capable of doing many of the same things, and have directly written multiple bridges and hooks and breakdowns.