Note that the corresponding change was made for checkboxes years ago, so I think it makes a lot of sense to do this for radio buttons to. This is code we have been using at the OU for ages.
For testing, you need to find a form with radio buttons that get frozen, and there does not seem to be one in the standard Moodle code (I searched for ->freeze). I suspect this only came up in an ou-specific plugin.
I you really want to test, create a test script with a form with a frozen radio button.
I think this is a worthwhile accessibility fix, so the pull request should be accepted, even though this bit of the API is not currently used.