You missed the point: they are talking about people who do not know those aspects of the LAMP stack, not the ones who can afford delegating them to DBAs and sysadmins. The first group are indeed glorified web page editors.

Again, bullshit. I've had PHP projects that were entirely command-line with no Apache and MySQL. If you want to argue that those projects weren't development, that's absurd.

Systems and database administration are hugely complimentary skills, but someone who doesn't know anything about setting either one up is still developing.

I agree with you in a literal sense. I'd add the adjective 'extremely poorly' to 'developing' for any developer who doesn't have a thorough grasp of the system for which they are developing.

An artist can make great art without knowing the details of how the dyes in their paint are manufactured. The same is true for development.

Can an artist make great art without knowing to use oil paint on canvas, instead of watercolor (or whatever - I'm not an artist)?

How about knowing the difference between types of brushes and what effect they have on the canvas? Is it 'great art' if it's accidental?

Yes, and yes.

That said, this is more like arguing that you can't be a great artist if you don't know how to make the canvas yourself.

Exactly. I'm trying to get into the state where the only machine where I have root is my phone or laptop.