This has been a common observation since time memorial: equivalent Mac systems tend to be competitive. Apple just doesn't compete in the very low end of the market at all.
Ok you might not have an air con, cupholders or a cd player but as MR Clarkson says "more powwerrrrrr"
Or as we say in German: Nur weil's hinkt ist's noch lange kein Vergleich :-)
This article only shows that equal Mac systems are competitive (cheaper). An equivalent, however, would be something completely different. No need to buy that exact GPU they have, for instance, when you could get equivalent performance for many thousands dollars less.
That leaves a lot of room for substituting components on the other side of the comparison, and you then have to add labor, warranty protection, assurance of compatibility for the whole (through system upgrades) and a really cool design and compact form factor.
If you value all of those things, the value is pretty awesome, but even if you value none of them it is still competitive. (Competitive does not mean "unconditionally better/cheaper" etc. It just means "able to compete successfully").