I think the reason is that the sho is advertised at 365 hp and you need to run premium to get it, and most sho customers know that they are supposed to get that much. Also you may lose 30-35 hp by running regular fuel in a boosted application and customers would cry foul if they lost that much, so ford has to disclose that info to cover their a$$. Remember the 99 mustang cobra that was advertised at 340 hp but the actual cars never reached that much, ford had to recall all of them and rework the engines to get the claimed power output, they wont do that again.
I also agree that the difference on a 2.0L 4 banger is not much, 5 hp at most. When I had my truck custom tuned on a dyno I got 238 rwhp on 87 and 250 rwhp on 93 only a 12 hp difference on a huge 5.4L V8. Factory tuning is very conservative, the gain on the focii engine is probably closer to 2 hp.
Triple MK3 Focus Sedans, a 12 Red Candy SE, a 12 Yellow Blaze Ti, and a 13 Performance Blue SE - 2013 Frosted Glass Escape Ti loaded
YBOG #01/L-CCC #18/HOIA #37