The default behavior is the "My billing information is the same as my shipping information" to be checked and the billing address form to be hidden.
Which behavior makes sense as default is highly dependent on the store and it's customers. Store managers should be given a choice which behavior they want as default.
In our industry our customers are not highly proficient with computers and are expecting to find a place to enter their billing information. They become confused and end up abandoning checkout or contacting support about it.
Add a pane option in the checkout flow to control the default behavior.
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It's likely this issue predates Contrib.social: some issue and comment data are missing.
At first glance the patch seems to be working. I can see the button unchecked and allows me to check it as "same billing as shipping".
It works as expected. I don't see any issues in code.