I think the only good argument against using the middle ring and small cog is the chain angle, the higher the angle the greater the friction and wear in the lateral sense. You've said several times that your chainline is fine in this combination and that's Ok with me. The argument is that it may be fine but not as good as a straighter chainline. If a cyclist is concerned with maximizing the life of the drive train components then maintaining the straightest chainline possible is going to extend the life of those components. But when you are in a situation where a quick one-step shift is more important then I say go for it. Or if shifting to the big ring and back to the middle ring means making multiple shifts just to keep a straighter chainline for a short distance, basically I'm too lazy or just don't have the time.

Sheldon's bike wisdom and advice has been a huge help to a lot of people including me, but I don't always agree with him and I don't think he expects everyone to agree with him all the time.

Al