I'm here to provide some insight about changing a customer's address.
You're on the right track. At this time, changes made in the main customer's profile won't flow to the sub-customers. You'll need to manually edit them to apply the changes.
I can see how having an option to update customer profiles by would make it easier for you, and others, to handle customer transactions. Rest assured, I'm going to submit a feature request from my side, which is sent to the Product Development Team. They're constantly looking for great ideas from users, like yourself, when deciding how to enhance QuickBooks.
Please let me know if there's anything else I can help you in the meantime. Thanks for reaching out, wishing you and your business all the best!