In this case, ActiveSupport::Inflector.camelize('active_support', :lower) is actually treated as the same as ActiveSupport::Inflector.camelize('active_support', true) (which is probably not what you expect!).
Just to confirm my understanding, is the suggestion here that ActiveSupport::Inflector.camelize either
Support :upper and :lower as arguments as well as true and false, or
Print a warning if the second argument is anything other than a boolean
I think both are reasonable and would lead toward option 1.