The bit about "smart developer quirks" looks suspiciously like the author only understands code that they have written, or is in a specific style that they recognize. That's not the biggest driver behind cognitive load.
Reducing cognitive load comes from the code that you don't have to read. Boundaries between components with strong guarantees let you reason about a large amount of code without ever reading it. Making a change (which the article uses as a benchmark) is done in terms of these clear APIs instead of with all the degrees of freedom available in the codebase.
If you are using small crisp API boundaries to break up the system, "smart developer quirks" don't really matter very much. They are visible in the volume, but not in the surface area.
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