Exactly - any announcement regarding the NPT gives the imperialists potential precedent for aggression against Iran, so Iran needs to maneuver their diplomacy to reflect their current concrete position in the conflict. Currently holding a large advantage allows them breathing room to make these public announcements. Further, the revamping of testing sites and lifting of missile range limitations are concrete preparations towards NPT withdrawal - Iran wouldn’t want to withdraw prior to developing the means of actually imposing their nuclear strength to the degree required to ensure complete sovereignty from aggression.