Not just general advice, but advice that is meant to be applied to TDD specifically. The principals of clean code are meant to help with certain challenges that arise out of TDD. It is often going to seem strange and out of place if you have rejected TDD. Remember, clean code comes from Robert C. Martin, who is a member of the XP/Agile gang.

The author cherry-picking one small piece out of what Uncle Bob promotes and criticizing it in isolation without even mentioning why it is suggested with respect to the bigger picture seemed disingenuous. It does highlight that testable code may not be the most performant code, but was anyone believing otherwise? There are always tradeoffs to be made.