I want to agree, but I think it's something far worse. Look at the original statement "Wouldn't the existence of "tools" only constraint DM and force them to play in prescribed ways", specifically it rejects and dismisses the very idea that rules are capable of existing in. Form that mechanically supports the gm or mechanically carries setting elements to lighten the GM's load. That might have been a reasonable thing to question decades ago, but we have plenty of examples from past editions like way 3.0 Ravenloft book did so by altering baselines or the way 3.5's rules for bonus types combined with the DMs best friend sidebar∆ to allow the gm something akin to on the fly rulings within the framework of a rule
∆you might remember it as the+2/-2 DMG section