Yes I do Nuna, because that is how a nuclear explosion is...

Yes I do Nuna, because that is how a nuclear explosion is instigated, by slamming two lots of nuclear material into each other at a great rate of knots!
The mach 5/50 tech would in my opinion lend itself very well to that, and "if" I am right?? then that would explain why both countries don't want to see it proliferate, for exactly this reason, and any of the stacked round technology irrespective of whether it was for weapons or for some other purpose like fireworks or the Pyrogen firefighting etc would have shown how the tech worked or perhaps even lent itself to modification for the purpose of building a nuclear trigger, I doubt either the US or Aus would want that!