This statement doesn't make any sense. It's hard to imagine that they don't have DNA evidence, which would be overwheming proof that it was Cayley.
They probably do have the DNA results, but are not releasing them as yet...........
Of course I am just speculating but perhaps they meant the clothing matched a picture of Caylee in the Anthony’s house so they meant this was the strongest evidence that the remains belong to Caylee without further testing?
It takes a while to grow the polymerase chain reaction (PCR) gels that give the gene information. That’s one reason these things tend to be drawn out. However, I think it takes 3-5 days, and then they have to analyze it, so for a high profile case like this I can’t see why it takes three weeks. One week should be plenty. Still, it’s very important. They don’t want to get it wrong.
Maybe they are hoping for a confession based on identifiable clothing in the bag.