Comment by jandrewrogers

The US started upgrading and modernizing its nuclear production capacity in earnest during the Biden administration, targeting a capacity of 80 weapons per year. It pre-dates the current administration by years.

This disclosure was pretty obviously intended to put international pressure on China to conform to norms on nuclear testing, while also letting them know that the US can detect their top secret nuclear tests despite their best efforts to hide them.

I'm sure the timing of the disclosure wasn't accidental but I don't see much nefarious about it. The US doesn't disclose their knowledge of this type of thing unless there is some geopolitical leverage in doing so, since it makes it easier for other countries to calibrate US intelligence capabilities.