TL;DR: you're looking for something which isn't there.
Art critics, like the Oracles of old, always sound like they're saying something, even something profound, but in reality, they never are².
After my comments, I realized I could never put it as clearly, plainly, and well as Orwell did in 1946¹.
So let me quote a part of Politics and the English Language, and let it speak for itself (all emphasis mine):
Meaningless words. In certain kinds of writing, particularly in art criticism and literary criticism, it is normal to come across long passages which are almost completely lacking in meaning.† Words like romantic, plastic, values, human, dead, sentimental, natural, vitality, as used in art criticism, are strictly meaningless, in the sense that they not only do not point to any discoverable object, but are hardly ever expected to do so by the reader.
When one critic writes, "The outstanding feature of Mr. X's work is its living quality," while another writes, "The immediately striking thing about Mr. X's work is its peculiar deadness," the reader accepts this as a simple difference of opinion. If words like black and white were involved, instead of the jargon words dead and living, he would see at once that language was being used in an improper way. Many political words are similarly abused. The word Fascism has now no meaning except in so far as it signifies "something not desirable." The words democracy, socialism, freedom, patriotic, realistic, justice have each of them several different meanings which cannot be reconciled with one another. In the case of a word like democracy, not only is there no agreed definition, but the attempt to make one is resisted from all sides. It is almost universally felt that when we call a country democratic we are praising it: consequently the defenders of every kind of regime claim that it is a democracy, and fear that they might have to stop using that word if it were tied down to any one meaning.
Words of this kind are often used in a consciously dishonest way. That is, the person who uses them has his own private definition, but allows his hearer to think he means something quite different. Statements like Marshal Pétain was a true patriot, The Soviet press is the freest in the world, The Catholic Church is opposed to persecution, are almost always made with intent to deceive. Other words used in variable meanings, in most cases more or less dishonestly, are: class, totalitarian, science, progressive, reactionary, bourgeois, equality.
† Example: "Comfort's catholicity of perception and image, strangely Whitmanesque in range, almost the exact opposite in aesthetic compulsion, continues to evoke that trembling atmospheric accumulative hinting at a cruel, an inexorably serene timelessness . . .Wrey Gardiner scores by aiming at simple bull's-eyes with precision. Only they are not so simple, and through this contented sadness runs more than the surface bittersweet of resignation." (Poetry Quarterly)
Let me re-emphasize that it is worth reading the entire essay, and actually, for the English language enthusiast, much of Orwell's work.
He was a perceptive thinker, who strove to live deliberately, and occupied a very interesting time. His circumstances permitted him to observe both age-old abuses of language, as well as new ones emerging from the burgeoning field of state propaganda (which we take for granted, and sometimes barely notice, today). This unique situation, combined with his nearly unparalleled skill in clarity of expression (borne of a lifetime of deliberate practice), resulted in a body of work which is not only interesting in its subject matter -- still relevant today -- but eminently readable. Quintessential food for thought.
¹ Anyway, if you're not convinced by Orwell, allow me to submit @Lambie's answer in support of my position.
That answer is clearly an earnest, genuine attempt to exegesize (is that a word?) "un-work" from the perspective of someone obviously schooled in art as a discipline. Lambie goes to some lengths to communicate what they took away from the passage, using a series of possibilities, generalities, allusions, emotive language, free-association, and additional neologisms, but primarily contradictions (i.e. definition by exclusion, because definition by inclusion is not possible, which is the problem).
As an effort, it is (at least partially) successful: in a sense, it conveys what I imagine was going through Whybrow's mind as he was writing the passage. Maybe. But its true merit lies in its ultimate question: Does this 'un-work' work for you?.
Interpretation of art criticism, just like interpretation of art, is a ineluctably private and individual effort. Because absent that digestion, reflection, and personal determination, it is meaningless. Just like art.
² And art critics' augeries are vague and yet gravid for the same reason the Oracles' were: it's too risky to one's career to place bets on just one outcome, but you still have to make a living.
Oracle: You shall emerge from your battle with the Romans victorious.
[later]
King: But the Romans won!
Oracle: Yes your majesty, just as I predicted: You shall emerge from your battle with the Romans victorious.
