You are correct, loyalty should be, and was, the sole criteria for clearances. This article refers to new rules which the others didnt.
You and the others might enjoy reviewing a few of the cases involving security clearances. You will note, in the past, clearance was withheld when an individual acts in such a way as to indicate a preference for a foreign country over the United States. Yes, the EXERCISE (voting, use of passport, military service etc) of dual citizenship could be an issue. If you read the decisions, you will note that in the case of Israeli dual citizenship, use of the passport is not an issue, since it is required of Israeli citizens to enter or leave Israel, and military service is generally not an issue for the same reasons. And among the mitigating circumstances that would allow the granting of clearance, dual citizenship is based solely on parents' citizenship or birth in a foreign country, exactly the circumstances we are discussing.
Without even being aware of these cases, a cursory reading shows that what I wrote above is pretty much how these things are handled. Each case turns on facts and not on a simple idea of being a dual citizen.
I wish you had posted this yesterday and saved me the time.