I have to respectfully disagree with you on this. As you said, the razor is canted towards the concave side making it difficult to shave properly with the convex side. The issue is we all are looking at this as westerners and don't and can't fully understand the whys and wherefores of this contraption so we try and westernize its use to suit our experiences.

The fact is the thing is designed to be used a certain way and certainly you can use it any way you wish but its no different than using any other tool and not understanding it and using it improperly but taking the attitude of well it works so it's right for me.

Saying that they were designed to be used by barbers in giving shaves to others is like saying cars were meant to be driven by chauffers not owners.