Would you be interested in changing the default behavior and making the CaptchaField itself handle the validation of the submitted data?
I'm happy to contribute this but of course it would be a backwards incompatible change.
Here's how django-recaptcha handles this:
https://github.com/django-recaptcha/django-recaptcha/blob/060ea47b6735f5d1f75d010a6c5b3f5aff5d13c2/django_recaptcha/fields.py#L78
Here's the documentation on def validate:
https://docs.djangoproject.com/en/6.0/ref/forms/validation/#form-field-default-cleaning