Another argument for birds is that the relative positions of the individuals in the group are changing quickly and substantially. A drone swarm almost certainly wouldn't be programmed to behave that way.
My aging ears that have been around too many loud motors, loud music, and loud shotguns can still hear a Mini 2 at 400 feet if there's not a lot of ambient noise.
I wouldn't rule out cold days entirely. There are folks on the forum who fly actively in Alaska and similar climates throughout the year. Just watch for periods when the wet-bulb temperature is near the dry-bulb temperature, i.e. very high...
I just checked the Mavic 3 Pro & RC Pro combination. As @Ralph thompson said, the update isn't available for the RC Pro yet. The most current version is 1.17.7. There are frequently lags in releases for various controllers.