"That‘s the respectable view of an engineer, but probably not the one of a musician who probably associates huge movements with increased volume and musical expression while returning to a default position is associated to silence."- ThierryThis is my view as a lay Thereminist. And with my instrument set to closer = louder my resting position is also silence. IMO if large volume hand movements are necessary then the instrument itself isn't very good. There is a happy medium to be found between flapping like a bird and too tight.
To me as well the common behaviour is natural. When volume is max you can freely gesture in addition. This can be seen in many videos. If volume was max in the down position one has to freeze. Of course a thing of personal preference.
Btw silicone hose over the loop would add some soft and matt aesthetics.