As a TA, I think having to download and grade student-uploaded Word files causes tons of issues and is convenient. I potentially grade the wrong submission for a student. If they save as a PDF (which Word allows you to do) then Labflow works joyously.
Can we either convert Word files coming into labflow to PDFs server-side, or render word files in Labflow in-line just like PDFs, or perhaps at a minimum reject the ".docx" file type with a dialogue box that tells the student to use Word to "Save As..." --> "PDF" (or use an online word to PDF converter).