[BugsJustFindMe]

> It takes well-calibrated electronics detonating conventional explosives with precise timing to set off a nuclear warhead.

The need for precise control and timing is true for plutonium implosion-style devices but not true for uranium gun-style ones. Gun-style detonators just need to smash two lumps of uranium together. You better hope the interceptor completely demolishes the aforementioned lumps of uranium instead of ramming one into the other.

[OkayPhysicist]

We're not that concerned about uranium gun devices, because they aren't really worthwhile to make. Their yields aren't high enough to justify the cost relative to conventional weapons. And explosive disassembly of the device is still likely to cause the nuclear element to fail. There's a reason the world basically gave up on them.