I'm not sure why that is your main take away from that article. The point is that relatively slow disk controllers designed for rotating magnetic storage are a

I'm not sure why that is your main take away from that article. The point is that relatively slow disk controllers designed for rotating magnetic storage are a bottleneck when you connect fast enough Flash storage. Connecting the storage via PCIe alleviates this bottleneck, to the point that you are no longer bound by the traditional constraints of small caches and large, slow permanent storage.