Hi, I was trying to adjust the configuration of the Clientside Validation module and ran into the same issue - I expected the class 'cv-validate-before-ajax' to cause a change in behaviour when add to the form, not an element. This is because on the configuration page for Clientside Validation jQuery it says "All forms with class "cv-validate-before-ajax" will be validated by default".
When I went looking for more information, I found the issue where this was worked on → , where I felt the discussion also implied that the class should be applied to the form. It wasn't until I found this issue that I realised that it just doesn't work that way.
For me, it would be preferable to the class to trigger the expected behaviour when attached to the form. I would find it very useful for the feature to work as described.