I wonder if there isn’t a stable chamber shape that promotes turbulence in a controlled manner in order to prevent it getting out of hand? A little bit like the dimples on a golf ball create micro pockets of turbulence promoting laminar flow.
That’s alright, fusion is only ten years away!
TV’s and plumbing are still measured in inches in the UK, the measuring system was already in place when we went metric and it was what people were used to. Plumbing fittings are as you said now rounded off to millimetres etc. but the actual physical size is still the same as the original imperial. For example what is referred to as a 25mm fitting is actually one inch (25.4 mm).