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7 days agoI’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.
Not an expert by any means, but I’d guess that has to do with the distinction between being on top of something, and having boarded something. You are on top of a (small) boat or motorcycle, but within a car. These examples refer to position. You can be both in or on a bus, plane, or yacht, because you have boarded the bus, plane, or yacht, and thus are “on” it, but are located physically within the vehicle and so are also “in” it (in the case of a yacht, that may depend on whether you’re inside it or on top of it). These examples refer to both position and state of existence.
This is totally conjecture so I’d be very curious to hear from an actual expert.