The other way to interpret these facts is that it takes a lot of work to actually detonate a nuclear weapon, so they are pretty safe by default and can handle abuse.
As an example, an implosion type bomb needs to be detonated at several places around the bomb simultaneously. It's designed such that if you don't have detonation of the explosives all at the exact same time then the pit won't make a nuclear blast.
They're very safe in terms of accidental nuclear detonation, but still, if the explosives are detonated it's going to make quite a mess to say the least.