When they have all the components manufactured and the enriched Uranium in “nuke shape” then y would also say they are developing one.
But while nukes arent that complicated to build in principle, there still goes quite some trial and design efforts into it.
This most likely includes doing tests with causing a nuclear explosion. Such tests would be detectable and a certain criterium for an ongoing development.
Remember how NKs nuclear weapon propgram got a lot of attention some 10 or so years ago? We knew because the seismographs picked up the shockwaves of underground explosions.
By that line of reasoning, they could have all the components of a nuke, and not actually be manufacturing one until they bolt it together.
When they have all the components manufactured and the enriched Uranium in “nuke shape” then y would also say they are developing one.
But while nukes arent that complicated to build in principle, there still goes quite some trial and design efforts into it.
This most likely includes doing tests with causing a nuclear explosion. Such tests would be detectable and a certain criterium for an ongoing development.
Remember how NKs nuclear weapon propgram got a lot of attention some 10 or so years ago? We knew because the seismographs picked up the shockwaves of underground explosions.