I suspect that recommendation is aimed at large apparent text size, making it easy to read, on typical monitors without scaling.The AOA recommends 20-28 inches, which isn't significantly different. Since I have somewhat worse than perfect vision(20/30) I sit a little closer than someone with perfect vision would, just naturally. 18 inches away when sitting up and attentive on something like a game, and closer to 24-26 when leaning back and viewing video or scanning over code etc.
This paper suggests that farther is better, and that ideal distance is in the neighborhood of 35 inches, based on the vergence resting point of the eyes. Of course that means you need a larger monitor or turn up the scaling to keep text size comfortable.