I appreciate your opinion, and accept that Bolt may have been able to be good at the 400m had he trained for it. I accept this notion, albeit with less sarcasm than you.
On the race:
Firstly the trackside clock is straight up wrong. The winner is outside 3:05 you can time it yourself. On Bolt's All Athletics profile it gives his team's time as 3:05.77 and they were about 0.2s behind the winner.
The time of '43.58' is completely unverified and I doubt this meet had electronic splits for each runner, and even electronic splits can be a bit dubious at times.
As for Bolt's split, I doubt 43.6 is accurate at all. I will detail my reasoning as briefly as I can below.
The runner who Bolt never caught ran a 46.4. If we assume Bolt started at the same time as this runner (he didn't) then Bolt crosses the line at 46.9. That makes him 0.5s behind at the finish.
We cannot see exactly when Bolt crosses the 400m mark from the video but we can see when the runners pass a camera tripod around 25m from the start line.
Bolt is 2.7s behind at this point.
Of course, we miss the first 25m so we cannot say exactly how much time Bolt has made up in that period. What we can say is it is not the ~0.65s required to make Bolt's 43.58 a possibility.
For one, it takes Bolt the remaining 385m of the race, when he is at his full running, to makeup 2.2s on the leader. There is no way he made up 0.65s in the first 25m. I don't need to do the maths.
Secondly, just for fun anyway, the leader passed the tripod in 2.8s. That means the leader is running at about 45 flat pace up to that point (makes perfect sense). Were Bolt to cover the first 25m in under 2.2s then he would be running at 34 second pace for 400m. Bit unlikely.
It is more reasonable to say that Bolt made up under 2.4s across the whole race. So Bolt's real split was a very low 44, likely 44.1 but could be as slow as ~44.2
That is a mighty fine run, he makes up 20 metres over 400m, which is huge. It is not 43.5 however.
Now a low 44 relay split, with a rolling start, for a 45 low guy is not out of this world. I'm sure you see that in the NCAA even.
I am sure Bolt could run a low 44 with some training, like I said. It falls perfectly in line with his other times from 100-300. His 300m is dramatically slower than his 200m when compared to MJ. That sets him up much worse for the 400m.
Also let's not forget how little the gains over 400m are at the very highest level. It took MJ 9 years to improve from 44.2 to 43.2.
I think there are others on the circuit right now that would beat Bolt regularly were he to have moved up. And I think Van Niekerk has a much better shot at the WR than Bolt ever has.