`@model.toJSON()` is being called and passed in to the template by default.  If a template helper is used, `@model.toJSON()` is passed to the template helper first.  The returned result is merged into the original `@model.toJSON()`.

I've removed the code that passes the data into templateHelpers and made the necessary corresponding changes to match Marionette's behavior, although this does result in extra calls `get` and `toJSON` calls.