If memory serves, I picked up strictu dictu from an article by the philosopher C. B. Martin. It struck me as a bit odd, but having found it in use by other good writers, I started using it myself. Using it, I am in good company. But classicist Mike Gilleland, who knows Latin much, much better than I do, considers it not a proper Latin phrase at all. See An Odd Use of the Second Supine and More on Strictu Dictu.
So I am inclined to drop strictu dictu. I should take the advice I myself give in On Throwing Latin ( a most excellent post that I cannot at the moment locate). I do strive to practice what I preach. But I will continue to pepper my prose with the unexceptionable mirabile dictu, horribile dictu, difficile dictu, and the like, ceteris paribus of course. And I will not apologize for my use of 'big words' such as ambisinistrous, animadversion, preternatural, desueteude, incarnadine, inconcinnity, unexceptionable, et cetera. Am I writing for a pack of idiots?
"Why not forget the foreign ornamentation and just say what you want to say clearly and simply and in plain English?"
Well, sometimes I do exactly that. But I refuse to be bound by any one style of writing, or to pander to the appallingly limited vocabularies of my fellow citizens. George Orwell and others who reacted against the serpentine and baroque sentences of their Victorian fathers and grandfathers went too far in the opposite direction. And now look what we have. For a poke at Orwell, see here. Zinnser I criticize here and here.
It just now occurs to me that it wasn't strictu dictu that I picked up from C. B. Martin but holus bolus. Holy moly, that too looks like bogus Latin. Perhaps the estimable Dr. Gilleland will render his verdict on this construction as well.