The following plumbing performance charts and graphs from XRP Fittings reinforce what Morris is attempting to share with us. The first chart is a pressure drop chart showing how much pressure different AN hose diameters cost you. Because of the way the CC website works, I'll post the forged vs streamline graphs in the next post.
In the chart below, you can quickly see that an AN-10 line vs an AN-12 line at 20 gpm (possibly a little low, depending on your
oil pump). I measured the ID of one of my AN-12 bulkhead fittings, and it is 0.627 inches, which is a close approximation of the 0.63 inches in the chart. A straight AN-10 coupling had an ID of 0.497 inches which is again a close approximation of the 0.50 inches in the chart.
The XRP research tells us that the pressure drop per 10 feet of hose with a 0.5 inch ID (AN-10 stuff) is 49 psi at 20 gallons per minute. The same pressure drop per 10 feet of hose with a 0.63 inch ID (AN-12 stuff) is 19 psi or less than half of the -10 line pressure drop.