That explanation makes no sense. There are many mini PCs of the same size that have their power button in an accessible location.
The excuse that most users never use the power button is the "you're holding it wrong" of 2024. Stop telling me how to use your devices, Apple.
The explanation mentioned on several forums that it's a cost cutting measure to avoid extruding yet another hole in the aluminum case, or routing the power cable, makes no sense either. This is a state-of-the-art machine, yet they're cutting costs on such trivialities? Give me a break.
This is unequivocally poor design. Yet Apple will never publicly admit that, and will gaslight everyone to think it's actually good, as they usually do.