Thanks for posting that pic, SlavaB. It clarifies a lot.
So, assuming there's no other important info in the stuff that has been cropped out -- which is a massive assumption -- it seems to be saying ACEA and API specs are only recommendations in case you want to go for the best possible fuel economy.
The difference in those recommendations is not surprising for turbo vs. NA. Turbo means more heat, so the minimum viscosity is higher -- 5W-30, vs. 5W-20 for the NA engines.
It looks to me like:
1. They think ACEA A5 is the ideal spec for all their engines;
2. They also validated API SM oils in a lower viscosity for their NA engines to give people more options, but didn't bother for the turbo engine because they feel it should run at least a 5W-30 and ACEA A5 5W-30s are everywhere; and
3. They're pretty sure their engines will run acceptably with just about any decent remotely-modern oil on the market, as long as it's in one of those viscosity grades.
So yeah, if you're using Mobil 1 5W-30, you're doing the right thing.