Thank you for your post. TestRail does in fact export all steps into the same cell. Exporting test cases from TestRail in CSV format is better used for sharing test case data or for local usage. If you are wanting to export test cases from one TestRail instance to import into another, the XML option is the best option to use. XML exports will maintain the section/subsection hierarchy that may apply as well as keep your test case steps separate.
Additionally, only the XML import supports updating existing test cases. The CSV import would create new test cases. That being said, we do have a feature request open to include test case updating via CSV import. I would be happy to add your vote to it.