Conclusions are similar to this video from Berm Peak channel, that could find goof helemts (in terms of protection) at low price.
However he advises to be aware of the existence of helemts on amazon that would not protect at all!
https://www.youtube.com/watch?v=ZKbYaOiz5U4&si=ElUomVmD-v9osmB4
Just guessing: trying to minimize vortexes and turbulences.