So, it seems that appending a checked radio input into a disconnected tree doesn’t update the checked state for other elements in the same radio group. Oh ugh, if it is appended to a disconnected form, the checked state for other elements in the same radio group does update.
Bug 1938489 Comment 12 Edit History
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So, it seems that appending a checked radio input into a disconnected tree doesn’t update the checked state for other elements in the same radio group. Oh ugh, if it is appended to a disconnected form, the checked state for other elements in the same radio group DOES update.