It's a fair question. They were foreigners submitting to an American journal, so there is always the possibility for some sort of cultural misunderstanding in addition to any language difficulties. Nonetheless, the journal's submission process provides authors with a page listing ethical standards they have to follow, and it says that plagiarism of any form is not allowed. In fact, this journal's particular set of standards even mentions that authors cannot copy anything obtained during the peer review process without the "explicit permission" of the reviewer. So I just expect them to follow the rules that they were told about when they submitted the paper.
So, I understand how it's plagiarism, but I'm still not following why your suggestion, with the goal of helping them get their paper accepted, wouldn't be acceptable to copy/paste. It was to them and only to them, so it's not like it's a piece of substantial work from another team. Seems to be an extreme form of following the letter of the rule, and not the spirit of the rule. But, I'm not an academic so I don't really understand this sort of lack of discretionary allowance..
I'm fully on board with fighting plagiarism down to that level.
But that said, I've often times wondered if this requirement of having to "rewrite in your own words" may do a lot of harm too. It obfuscates that things that people are talking about are actually exactly the same, or make it fuzzy what the exact differences are.
In a particular academic CS area I've witnessed people reproduce again and again the essentially identical description of setting and assumptions, but in being afraid of plagiarism accusations, they over and over re-formulate things which made it nonobvious that things are the same as from other authors or even from their own earlier work.
