Unfortunately this isn't consistent with how these terms are typically used. This article only explains the simple case where your program is small enough that you can compile all source files at once. That's not realistic or practical for much larger projects.

Both WebKit and Chromium support unity/jumbo builds. They combine around 20 source files at a time into a single compilation unit, which provides a reasonable tradeoff - making the full build noticeably faster without overflowing RAM and without making the cost of recompiling after a single change too large. You also get lots of parallelism.

Making a unity / jumbo build work for a project with 10,000+ files and millions of lines of code is not simple at all.