I had a chance to test out OP with firmware v01.09.00.20 at the weekly Friday Night Fireworks at Hilton Hawaiian Village. Video was shot in 2.7K/30 fps. Was there any improvement? You be the judge.
This fireworks was before the recent firmware update.
Now that is really interesting because it's close to stereo considering the mic positioning. I had a similar outcome once but most of the time it's not as clean or open. Nice.
We reduce the triggers of af-c when the firework is detected. When recording firework, AF pumps will almostly never appear. For night scence(firework, LED etc), it is very important to take a clean video. Thx for your share.