If you read the original post, 3/4 of the "computer" in the Studio Display is power-supply - 24" iMac has an external power brick.
Also, on the 24", virtually the whole "computer" is in the chin and uses the full thickness of the case - and the fans are either side of the M1, blowing air directly over the M1's heatsink.
Everything in the Studio Display has to fit behind the display panel. It also looks to me like the components are very spread-out - possibly to keep everything thin and avoid any "hot spots" affecting the display. I guess it's using the back panel as a heat spreader... If the article is right about where the A13 chip is, then the fans are nowhere near it - but then it's an iPhone chip and since when did an iPhone need a fan?