Duplicate word removal seems like a naive, coarse grained method to improve writing style.
Smells like the high school trope of throwing a thesaurus at your essay and hoping for the best
Still, sometimes recognizing duplicate words points out some bad/imprecise wording where you're repeating yourself and may not like that.
I find myself using the "edit" feature on comments online a decent amount to catch/add things I only found when reading it back in complete form.
I do like that it lists them on the side, and allows you to remove them.
Most educational literature from the US are rife with sentences that might not be verbatim repetition but most certainly say the same with a different word soup.