Does the fact that engineers have to eat change the nature of engineering fundamentally if the way they are able to eat changes?
That nature of engineering is practical application.
What engineers are focusing on is what they will build. If they're at work building iOS apps for commercial purposes they aren't going to be building and publishing as many open-source libraries or tools. This affects the entire ecosystem of engineering. It affects what kinds of tools and libraries get built. Tools and libraries are "the nature of the practice". You don't program in an object-oriented manner without having an object-oriented programming environment.
As for art, if you're not getting anyone to pay you for what you're making, you're gonna have to get another job. This is gonna have a big affect on what and how you make things. You might respond by working as little as possible and using cheaper materials. You might work a bit more but have a less time consuming process. You might be able to find commercial work that utilizes and promotes your artistic skills. No matter what, your process and therefor the kind of art that you make is gonna change.
The author wants all artists to be like Elon Musk, in how freely they can pursue their craft.