One of my jobs recently had a paragraph with three sentences: the first used “surge’, the second used “urge” and the third used “surge” again. We’d used “surge” already in a previous paragraph and were to use it subsequently so I changed the above to “spike”, “encourage” and “sharp rise”. Sometimes, repetition of a word can give emphasis and offers a certain poetry. However, in this case, it just appeared that the writer lacked the vocabulary to describe the situation.
You don’t need to be a walking thesaurus to be a good proofreader but having a good vocabulary means you can add value to your client’s work.