DOCX reader could treat the selection of "special formatting for the first column" as "the first column is a header". Minimal Working Examples table-2x2-single-header.docx table-2x2-two-headers.docx ...

I believe the problem is caused by the last row []] in the 1st native. The pandoc docx reader somehow treated the 1 row table as a header row with empty body. By the way, as a general rule, is it safe ...