Hard disagree. The fact that they have customized their system to such a degree shows they do know how to use computers. I think you're trying to conflate that with other things like programming ability, which are orthogonal.
I can adjust my car's interior temperature to +/-1F and play music from my phone, but if you think that makes me some sort of auto mechanic genius...
Wrong. Knowing to customize a theme != knowing to use a computer != knowing how computers work.
I can say I know computers and how they work pretty well, but these days I have much better things to do to learn the best way to themes my shell so that it matches my waybar, and that both switch colourscheme when dark mode activates. I could learn if I wanted, but I’m not a teenager anymore; I don’t care. Incidentally, when I had the time concern myself with GTK themes and wallpapers and Compiz, my knowledge in computers was a tenth of what it is now.
It would be like saying a car decorator is the most expert of mechanics.