Inconsistent property of div that wrapping hidden fields in forms

From the generated forms using CForm, I see there are two hidden fields generated by CForm#renderBegin - one is the CSRF token

<div style="display: none;"><input type="hidden" name="YII_CSRF_TOKEN" value="471d426ac9f5731d54108bca4b54af8bfd2cac64"></div>

another is the form unique id

<div style="visibility: hidden;"><input type="hidden" id="yform_c764d35f" name="yform_c764d35f" value="1"></div>

which IMHO should made as display: none instead of visibility: hidden, like the first one