I made reference to this in my reply about radio and checkbox rows, but this is actually an issue that's more general than the specific instance noted. It's actually the same issue as the custom field label association bug report but I'm leaving them separate as the custom field one is a much more complex version of the basic issue.
Essentially this comes up where we've manually built complex form rows. Basic rows will have the necessary associations done automatically. If we needed something that didn't fit one of those (which is caused by the related checkbox here), then we will need to handle these associations manually. I've identified a wide variety of examples that could be improved, though the process may vary for each. Some may need manual label association while others will need role=group + aria-labelledby along with extra aria-label entries.