Ok, no... 8 GPU is OS (Windows) limitation not the motherboard. If you have used this motherboard then you would know that it does not POST (boot screen with company logo does not come) if you put more than 13 standard (non mining) GPU. Now, my post has shown that it can work.
Yes, 6+ rigs on vega need not be considered (due to power consumption and other reasons), but RX 500 or RX400, or NVIDIA's 1060, i would slap on 12 if not a 19 rig blindly to maximize PSU utilization.
Finally, reason why people are so pissed about this board is because Asus advertised this as 19GPU rig without making the terms clearly (terms where you need mining graphics card for more than 13 gpu).
As a customer people have right to return the product if they are not satisfied with it. Don't see why would people be pissed on Asus if they didn't read exactly what they are buying. Manual can be downloaded without any obligation and on page number 16 you have this picture:
Currently this board is on waiting list so I am almost sure if someone returns his board it will be sold few hours later to someone else.