It's very clear what's happening: they're passing it through a writing tool that has an "Auto-improve" feature the users click. This would do the naive, pre-LLM, trick of taking "repetitive" vocabulary and varying it using synonyms.

I assume it is due to machine translation? I do not see mentions of "failure" at all, which would be expected to exist if it was to increase variety.

I think (heard) some used to translate an article back and forth a few times to get a "new" article, but maybe it could have been some kind of "paraphrasing" software like you describe (but for avoiding plagiarism detection rather than repetitions).