Unable to upload docx saved with libre writer my organization automation portal

I have saved the attached lms-docx-upload-libreoffice-save.docx file with libre writer and opened it in MS word and saved as lms-docx-upload-msword-save.docx . I can upload (attach) the MS word file to my organization automation portal fine but when uploading the libre writer saved file, the website gives error:

“file extension is not consistent with the file content”

lms-docx-upload-libreoffice-save.docx (5.0 KB)
lms-docx-upload-msword-save.docx (11.0 KB)

The file type is definitely DOCX (OOXML) - you may check the ZIP package. Word has no problem with the file. So the question is: what broken logic does the (unknown) portal software use to check if that is indeed the consistent content?

@mikekaganski How do I know?