I’m shocked no one else pointed this out. This isn’t a rule of grammar — this is a style rule, which isn’t actually part of the English language. Different style guides recommend different things. This happens to be specifically delineated by American/Canadian style guides vs British/Australian style guides; however anyone could publish a style guide. If USA Today decided to make and publish a style guide that they used in their articles that said there should be periods both within and after a quote, that would be valid by that styleguide.
I’m shocked no one else pointed this out. This isn’t a rule of grammar — this is a style rule, which isn’t actually part of the English language. Different style guides recommend different things. This happens to be specifically delineated by American/Canadian style guides vs British/Australian style guides; however anyone could publish a style guide. If USA Today decided to make and publish a style guide that they used in their articles that said there should be periods both within and after a quote, that would be valid by that styleguide.