However, that is not nearly adequate. A moderator does not see what has changed. Also it could be used as a timed-attack. Insert it now and report in 2 years. That is another reason why this thread is bullshit. Imagine if we just banned you forever, philipma1957, because you plagiarised some random post 6 years ago?
From my experience - if the edit timestamp is later than the other post, the report will be marked as "bad" regardless of what actually was edited. Even if it's not, that would be a very easy appeal.
Technicalities are not an issue. It's a bit more murky when it gets to
intent (was the user blatantly copy-pasting, or paying homage?), which is where mod discretion comes in.