That's not to say that natural phenomena (other than jokesters and other creative types with too much time on their hands)
can't create some sort of imprint...
I'd say taking millions of abductees and unknown numbers of mutilated body parts excised with the person conscious without anesthetic . . .
would be a great deal more violating of such a directive--as well as the treaty they signed during Ike's years--which we later found out they were violating wholesale.
I personally think any noise about a prime directive is largely hogwash or limited to a minority of the ET races. Plenty of them seem quite comfortable being quite terrible to millions of humans. I forget the likely statistics but something over 3 million people are likely to have been abducted according to I think a Harris pole surveying for key factors historically and reliably associated with such--even with people who have no memory of such.