@Bussty
It's the same sort with the specifications of flight time, it's theoretically.
Technically, under ideal circumstances, 12 km are certainly possible (I would even believe a bit more), but from a practical viewpoint, with interference, terrain, weather conditions, etc. this may vary dramatically.
With the differences in design of the drone and the controller, it may be obvious to explain, why a reduction in range is explainable. It might also be the case, that with the beta firmware DJI has reduced the signal strength or any other parameter in this matter. We simply don't know.
There have always, ALWAYS been these discussions about reduction of range and the fear of poor signal with any new drone.
I am flying in Europe where we have the weaker signal output, not the FCC mode, and I only had problems with the signal, when it completely derived from the above given circumstances: terrain, interference, handling error.
I simply can't see, why DJI should drastically worse their O3 transmission (bugs aside).
At least one reviewer said (51 Drones), he experienced better reception than with any of his other drones (out for about 1 km). So, there's that.
It's too early to tell and a bit of a neglectable worry in my opinion for most of daily flights.
But if you are hunting the next record or fly in areas with heavy congestion, external antennae would possibly the way to go.