[unheardPartner]

Maybe they thought it would be worse if someone found out and it was exposed that they didn't cite their source.

[kolinko]

It's not a source in this case - if I understand correctly, they used ChatGPT to rewrite a message written by them.

[trpv]

I understood it differently. Saying the email is a “paraphrase from ChatGPT” seems more like they had ChatGPT generate it, and then modified or “paraphrased” it themselves