Readability can be quantified and it done by static code analyzers into a metric known as cognitive complexity [0], which measures things like amount of branches in your function. The thing is, you can make code of low complexity but still hard to read.
Cyclomatic complexity is a good metric for local readability, but for considering the readability and ease of modification of whole programs or even for single files, it's far from good enough.
For an extreme example: you can turn all the methods of a complex program into one-liners, and all your classes into one-method classes. But doing that will definitely make your program harder to read.
Sure. You can trace branches to quantifiable roots, but you can’t trace readability. To me, readability means something different than what it means to the author of that article.
[0] https://tomasvotruba.com/blog/2018/05/21/is-your-code-readab...