The reviewer presumably used the zero-setback seatpost to change their saddle position.

KOPS is a rule of thumb often used for initial fit of road bikes, but there's nothing fundamentally "proper" about it.

Saddle position needs to allow the rider to pedal, and posture them reasonably for the riding they want to do on the bike in question. Laid-back cruisers often have the saddle much farther back and lower than KOPS in order to position the rider upright and put all their weight on their butt; TT bikes often have the saddle farther forward than KOPS so that the rider can maintain an open angle between legs and torso when their posture is low and aero (and they use aerobars to make it easier for the upper body to support the resulting weight over the upper body).

If you're able to achieve the saddle position you like on a non-zero-setback seatpost, then you probably don't need a zero-setback seatpost.