[banachtarski]

It should absolutely pass the sniff test.

The cost isn't the cost of parsing. It's the cost of compiling something you've compiled before. If you change a header that is included in N translation units, you compile N translation units, even if you didn't fundamentally change the header contents in a way that would effect the final object files.

[PaulDavisThe1st]

But that isn't a cost of the preprocessor. It's the cost of definitions (and declarations in some cases) living somewhere other than the compilation unit in which they are used.

Even with a "module" system as handwaved in TFA, there's still the possibility that you (or someone else) changed a "module". C++ makes it almost impossible to decide if the change requires recompilation (without effectively doing the compilation to decide).