An artist who stops creating, or who doesn't create, is no longer an artist, in my opinion. Just like someone who claims themselves to be a baker but never actually produces any baked good is not actually a baker. The word 'artist' implies that you are a currently practicing producer of artistic works.
But to the titular question, I don't necessarily think so. Like you say in the article, there's a plethora of reasons one might choose to stop producing art. Maybe they no longer find it the ideal medium in which to pour themselves and their emotional states into. Artistic expression is a great facilitator of emotional processing, but it's by no means the only kind. It's not like people who don't practice art in its many forms are emotionally dead. Everything in our lives is ephemeral. And of course, some people see art as a higher calling, some sort of eternal yearning for truth, something beyond themselves that they must get out, but I don't think that means it's the epitomic way for one to express themselves.
When I compose (my electronic stuff), I wouldn't say I even use it as medium for expressing or processing my emotions, not consciously anyway. It's usually more a case of a search for the ideal sound, the pinnacle of music that I'd like to hear. Most of the time I'm thinking in realm of what that idealised music sounds like - it's timbre, rhythm, it's style - rather than how I should best express 'x' emotion via sound. I'm trying to get the music I compose to make me feel something, anything. Sure, others and I can perceive an emotion in my music, and I'm sure what I compose is at times a reflection of my emotional state, but I don't use it as a tool for self-expression in that way. If I were to stop, I wouldn't feel like I'm committing emotional suicide, just that it's no longer providing what I desire from it. Perhaps that means I'm not being genuine or true to myself, perhaps that is what its missing, but that's how it is.
Honestly, I'm unsure of what I've written here, its a tad confused but I'm a generally confused. It's quite a tricky question under the surface and this is what came to my mind as I was reading this post.