I'm not sure I follow the thrust of the article. The author starts off with talking about clean code, but then compares OO with procedural code. It's not the same thing, and of course we've always known that OO abstractions carry a performance penalty. Even the founders of OO (Alan Kay et al.) acknowledged the memory and compute impact, but thought it was a worthwhile tradeoff for clean abstractions in complex code-bases.
Back then computers were far less performant than they are today, so the first languages (e.g. SmallTalk) had to be compiled into a bytecode VM that ran on a Xerox PARC. Other efforts included hardcoding some of the constructs into the ISA.
He states at the start of the article the tenets of clean code he's arguing against, not just the general OOP of it. Shows how ignoring a certain tenet leads to increase performance, that's the thrust of the article. He routinely in the article goes back to the tenets he's arguing against.