Since their initial description is rather vague (they even describe the area as "uncharted" though that's clearly not true), I can't say for certain whether this specific site is, in fact, previously known. That Franklin survivors would burn scarce wood as a signal seems a bit farfetched, unless they actually believed a ship to be nearby, and if indeed the site dates to the Franklin era, any grave would be "western style" since Inuit of this period did not build permanent graves of any kind. The tent circles could be Inuit; an expert eye would be needed to tell, and probably a closer site survey; bone pins suggest pre-contact Inuit, and that the site was in use well before the arrival of any Europeans.
On modern charts, the description seems to match the area of the Tennent Islands, the largest of which is Qikiqtarjuaq (not to be confused with the island of the same name off Baffin Island). And there is, in fact, an Inuit account of Franklin materials from this area; the Inuk Hall knew as See-pung-er (the same who was among the first to obtain materials from near Point Victory) said that "he had also seen a monument about the height of a tall man at another point between Port Parry and Cape Sabine." Hall asked him if he had torn down this cairn, and See-pung-er answered "only enough to find something within." This something, Hall was disheartened to hear, was a tightly-sealed tin canister which was "full of such stuff as the paper on which Hall had been writing," and since it was "good for nothing to Innuits" it had been given to the children, or thrown away. See-pung-er went on to say that he and his uncle had camped near the site, wrapping themselves in blankets they found in a pile of white men's clothing; he further mentioned that a "kob-lu-na's skeleton" lay nearby.
So the new "discovery" sounds to me very much like the same site, or one closely related to that seen by Grylls and his party. It's possible that some of the surface artifacts were unrelated to Franklin's men, but the description of the graves certainly sounds telling; they also saw a small scrap of blue cloth, which could be connected to the pile of clothing, or one of the graves. The site should certainly be visited by trained archaeologists, as there has not, in modern times, been any effort to retrace Franklin men's footsteps in the northeast area of King William Island, though it is fairly clear that some of them must have fled there, or paused in their flight elsewhere.
This story has since broken into the public press, with an article in The Independent on Sunday which gives Grylls' account in a way similar to when it was first posted on his own blog; the persons consulted by the reporter seemed to feel this was new news -- but in fact, as in so many cases, it's most likely a site already visited by Inuit early on after Franklin's men perished, and documented in Hall's notebooks.