By artificial, was he/she alluding to a post-recording in studio technique? Or did they just mean artificial by the standards of improper technique?
Improper technique, if I remember correctly.
He kind of implies that it is "improper" technique, but it really isn't. James manufactures his vibrato mechanically, and there are a variety of ways to do so. If done correctly,
none of those techniques damage the voice or are "improper" by any objective standard.
He says "Vibrato should never be a 'conscious choice'. It is a natural byproduct of healthy singing." That isn't really true. It
can happen naturally without the singer really trying to do that. But that is
generally only the case when one is singing in classical style (think true opera singers). Singers using a belting technique (the vast majority of pop, rock, and metal singers) or mixed voice will generally not get that type of natural, involuntary vibrato. That's just the physiology of the human body. Virtually every popular artist you have heard that uses vibrato, LaBrie and Dickinson included, consciously manufacture their vibrato. And, unfortunately, there are some voice coaches out there that will say that that is "wrong." But remember--just because someone happens to be a voice coach doesn't mean that their opinion is correct.
Bringing this back more to the subject, James has two things going for him that can alienate listeners. His timbre is very unique. And his vibrato, especially in a live setting, can be very extreme. The first issue is just his physiology and how that manifests in his voice. People like it or they don't. It just is what it is. The second is his choice of technique. It isn't objectively bad or good, although I think a lot of people will say they prefer a less extreme vibrato than what he sometimes does. His is definitely more extreme than Bruce's, so I get why somebody could like Maiden and not DT. It's just preferences.