[mdwrigh2]

That's not necessarily because you could do it in a single frame; a lot of the old touch controllers would maintain high levels of hysteresis as a really crude technique to mitigate low SNR. Couple that with a fairly dumb implementation of pointer tracking and you end up easily fooling touchpad into thinking the two pointers are the same. Note also that this is a much rarer and more user-friendly failure scenario than choosing to have the software err in the other direction (erroneously splitting a moving finger into two separate pointers, one of which may look like a tap gesture).

Source: I occasionally work with touchscreens, many of which experienced the same issue in early devices.