What engineer would design a nuclear weapon to power up when drop without the crew setting it to do so before hand!!!!!!!!!!!!!
I believe what they are saying is that, in the act of breaking apart, the disintegrating airplane's systems sent one of the bombs a "go" signal.
But there seems to be agreement from all the engineers that this bomb was a bad design
so far as these safety systems were concerned.
I question that any such bomb would be design to go off when it hit the ground as even from the first two bombs that was dropped on Japan they was set for an air bust at a few thousands feet.
You waste far far too must power of a nuke in having it going off at ground level.
Airbursts are a wonderful way to incinerate a population center. But groundbursts are often desired when attacking military bases.
Plus, even when a bomb is set on airburst, there is usually also a groundburst fuse active on the bomb, just in case the airburst fuse fails.
Even if what you really want is an airburst, if the airburst fuse fails and you have to choose between:
a) a groundburst, or
b) an intact bomb falling into the enemy's hands for dissection and inspection
.... option "A" is preferable.