Hi Jared,
I did a quick test, and it is possible to get the behavuour you want by using a "name" extended property and a group name or identifier as value. BUT somehow it seems that inside a TableRecords, the platform never assigns the specified Variable the Value of the Radio Button, so as I see it (but I don't have time to delve into it too much), you can only solve it by using an OnChange (something you specified you didn't want).
I did a quick test, and it is possible to get the behavuour you want by using a "name" extended property and a group name or identifier as value. BUT somehow it seems that inside a TableRecords, the platform never assigns the specified Variable the Value of the Radio Button, so as I see it (but I don't have time to delve into it too much), you can only solve it by using an OnChange (something you specified you didn't want).