You say that Radio Buttons are required by nature
and you linked to this document
However, they state that not all user agents behave the same way (Chrome for example does not set any radio button) and that you should make sure to set one radio button to "on".
That's ok, but you don't give a way in the form tag generator to set value "on" to a certain radio button.
(it means that it is possible to submit the form without setting any radio button)
Please add such feature so that we can always have a button set to on.