Here's Zdziarski's possible explanation ... [Most of the tech experts I’ve heard from believe the same as I do – that NAND mirroring is likely being used to some degree to brute force the pin on the device. This is where the NAND chip is typically desoldered, dumped into a file (likely by a chip reader/programmer, which is like a cd burner for chips), and then copied so that if the device begins to wipe or delay after five or ten tries, they can just re-write the original image back to the chip. This technique is kind of like cheating...