What do you guys think about it being just a timer?
The electronic components the FBI apparently recovered have been identified by the RC car manufacturer as pieces of their products.
Also, a timer is more problematic to deploy. Once you set the backpack down and activate the timer, you absolutely, positively, must put distance between yourself and the backpack (unless you are in suicide mode, in which case, why have even a timer? and why attract notice by setting the pack down?). Then, when time is up, it goes, never mind if that's the optimal instant.
On the other hand, with a decent RC system, you can get away, turn around, and watching the crowd, pick the optimal moment. And then look up at Lord & Taylor's cam and say cheese.
BTW, that AQ Chef article everybody cites does not cover using RC controls. It confines itself to the old-fashioned makeshift clock timer:
Very basic stuff.
A timer would overcome the problem of getting the radio signal through the steel pressure cooker.