I found when checking word count in a long document that Writer always was 10 words longer. I finally traced it to Writer counting some dashes as words. Neither MS Word nor Softmaker Textmaker reads these as words in their count. I can provide a document that demonstrates the difference, but it doesn't reproduce in an online form.
Steps to Reproduce:
1.Not sure how the dashes that are counted were made.
Some dashes are counted as words
The count should have ignored the dashes.
User Profile Reset: No
Created attachment 153059 [details]
Shows example of a dash that is not counted as a word and one that is.
In OOXML the run is "<w:t xml:space="preserve">Earth </w:t><w:softHyphen/><w:t>– not</w:t></w:r>"
Which on filter import to Writer gives a text run of U+0020 U+00AD U+2013 U+0020
So, seems the filter assigned U+00AD (SOFT HYPHEN) in combination with the (EN DASH) and bounded by spaces is treated as an edit engine word, increasing the word count.