What a dumb article. Sounds like an old C graybeard who's never understood the point of proper type safety or readable code. None of the performance gains the author talks about actually matter, whereas the entire point of clean code is to make it easier to read and maintain by other programmers. Let's also not forget this important quote from Donald Knuth: "premature optimization is the root of all evil".
Simply put, unless you're working in extremely resource-constrained systems, or have some code snippet being run an incredibly large number of times over a humongous amount of data, these kinds of performance optimizations simply don't matter and you get more benefit from writing the code in a way that reduces bugs and is easier to read. Heck, most of the time compiler optimizations make this entire argument moot anyway.