Not tautophrases but in the ballpark are I don't have any more information on that, which flatly pleads ignorance, and I'll have to get back to you on that, which gains the evader only temporary respite. Let's move on, previously the most popular refusal to provide more fuel to a continuing embarrassment, connotes, "I don't have time to waste on pursuit of this exhausted subject."
For additional nuance, I turn to Joe Pickett, executive editor of the American Heritage Dictionary.
"It is what it is is also a way of expressing philosophical resignation over a disappointment, of saying that the situation just has to be put up with. Athletes will say it about a missed catch or a bad call by the referee; it means that they don't want to dwell on the situation. A variation of It is what it is is What's done is done; you'd never say that about a person, but you can say She is what she is. It reminds me of a phrase rampant here in Boston: `That's just Manny being Manny,' to refer to the weird behavior of the Red Sox slugger Manny Ramirez. It must be a variation on `Let Reagan be Reagan.'" (That tautophrasal political slogan was based on the 1981 Let Poland be Poland.)
IIWII, to use space-saving initialese, has another sense of a mild put-down, as if to say, "That's all you can expect." A Denver Broncos wide receiver who was short on receptions last year was described in the sports pages of the Denver Post as having reached the "he-is-what-he-is stage." But another tautophrase intended to cut off further debate or questioning carries a powerful note of finality. The linguist Geoffrey Nunberg, whose book on right-wing rhetoric is coming in June, steered me to Chapter 19, Verse 22 of the Gospel according to John. The Roman Pontius Pilate, asked to amend the words he had ordered inscribed on Jesus' cross, rejected all objection with "What I have written I have written."
In these reflections on deflections, my favorite assertion of tautophrasal philosophy was by Popeye the Sailor Man in a 1930s comic strip by Elzie Segar: "I yam what I yam an' that's all that I yam!" (That statement speaks for itself.)
Will the vogue use of It is what it is become fixed in the farrago of unresponsive responses? The answer is in its own future tense, sung in the Spanish Que sera sera: "What will be will be."