Re: "it has low torsional rigidity"
I'm not an expert, but there are lots of debates on this subject.
Although I understand the reasoning as to why torsional rigidity is good but, there are lots of arguments against it as well.
Rigidity in any form is not good in many ways.
If I fully believed that, I would go with a low top flexible trail runner or even go barefoot.
I do believe that with proper conditioning, rigidity in any form is a handicap for many people.
Many of us urban types need rigidity because of our own personal limitations. Run barefoot over rough terrain for long periods and that will get your in shape. Rigidity in any form will no longer be needed as your feet will provide.
Many people who live without shoes most of their lives, or only with very thin flexible shoes, have no need for rigidity.
I personally need some rigidity but, maybe some day:-)