No I think they are suggesting that seasoned professionals should build illusions because that's what they do..You would not get a car machanic to work on the airliner you plan on taking on tour would you? Um no......But you know what I mean...
You can tell the difference between a pro built and a prop that came from a metal shop, I'm not saying that a magician cant build his own effects,
infact many big name illusionists do, but they take years, months perfecting mistakes a pro could have seen in the shop..

PS: I suggest anyone should try doing illusion design and fabrication, that's the only way we can get anything new........take chances.......