From what they were saying is it was him showing her how he was going to do it before they filmed jt
Given the described sequence of events, it sounds like the armory cart had three prop guns prepped for the scene, including at least one "cold" one for rehearsal and one "hot" one for the live take. The assistant director egregiously broke safety rules by not waiting for the *armorer* who actually prepped the guns to give Baldwin the correct one, instead grabbing the "hot" gun himself and erroneously announcing that it was cold.
This is also consistent with multiple reports that the AD in question had a reputation for being dismissive of firearm safety procedures, and even being fired from a previous project after he caused a misfire incident. That should have been a red flag even before the two prior misfire incidents on the set of "Rust".