That is in no way a wrong combo, I mentioned specifically it's a non ocing combo and nowhere did I mention i5 can't OC, I would rather prefer a great locked mobo with a locked or unlocked processor than a not so great unlocked mobo.
Getting a z mobo can't give you a good OC on its own, you'll need an af cooler which pushes the budget to 28k, while you won't need af cooler with locked mobo as you can't OC, and hence you're well in budget.
Moreover, Fx is in no way a weak cpu, OC it and it can max out any game, also it's considerably cheaper than i5 and the mobo I included with it is great for ocing. A better value for budget users, it can even outperform i5 in games like BF series.
Also, the mobo which you mentioned doesn't have the best thermal for ocing.
It's not between which cpu can outperform whom, but rather if he wants to OC or not, both cpu can smoke any given game with a powerful enough gpu.