Employee bank account primary flag

Summary:

When manually entering bank accounts in expenses, is the primary flag defaulted or does the user have click it manually? How does it work?

Content (required):

We want to enable an expense report validation that requires one employee bank account that has the primary flag. When checking all bank accounts the vast majority had the primary flag set.

Based on this I am suspecting that the primary flag is set per default. But I am not sure and would like to know if anyone has insights into this?

Version (include the version you are using, if applicable):

21C

Code Snippet (add any code snippets that support your topic, if applicable):