You keep bringing up examples where there were official documents drawn up and the Pope did everything through the proper channels to promulgate his decrees.
Ordinatio sacerdotalis was duly promulgated on Pentecost 1994, published by Libreria Editrice Vaticana, is available on the Vatican website as linked in many languages, and most certainly is a “a papal decree, a slip of paper with his coat of arms on it.”
This was a homily, it wasn’t a decree, a pronouncement, a promulgation, or anything. The mainstream media are the ones who did the publishing. If you think the Pope rules through the mainstream media then I am not sure what to do with you.
It is conceivable, though more or less preposterous, that the Pope could decide to rule verbally, and assign a secretary to write down everything he says that sounds like a decree and “make it so”. Of course, the Pope has not done this, or we would’ve heard about it. But in practice what happens is that the Curia draws up the documents and the Pope signs off on them, or sends them back with changes. It’s a bureaucracy and they run on lots of paper being pushed back and forth. The Pope has better things to do than spend all day writing or sitting at a computer, so his secretaries do the heavy lifting. But in the end, documents are always made and they always bear official insignia and authenticated signatures. They wouldn’t work otherwise.
It is conceivable that a particularly insane Pope could choose to rule verbally without appointing such a secretary, doing away with “the stroke of a pen”; he could abolish the printing of AAS, he could suppress L’Osservatore, he could shut down the Papal website and burn the Vatican Secret Archives. Then he could issue all his decrees on a plane to eager reporters who would duly publish them in Reuters, AP, and the L.A. Times. Thanks be to God, we do not have that kind of Pope. We merely have one who makes strong off-the-cuff comments in public.