Here's the problem with this "record"
With a random scrambling of the cube, some solves are easier than others, so it is chance if you get an easier solve that takes less time.
Back when the cube was new I got one and got a booklet that showed various "tools" (using the article's terms) you could use toward solving it - yeah I should have figured them out on my own, but I was an impatient teenager! When I got good at it I could sometimes solve in under 20 seconds, but usually 30 was my average. The fast solves were just lucky in that I needed fewer tools to unscramble it.
Obviously to beat 5 seconds you not only need many more tools than I was using, but to execute them faster as well. But it will still remain up to luck how many tools you need (or tools with fewer individual moves required than other tools) If he got a different cube it might have taken him a couple seconds longer, if someone else who is as skilled as he is (if there is anyone, maybe he's really the best but the record isn't 100% proof of that) got that same pattern they would have got a similar time and owned the record instead of him.
The 15 seconds of inspection probably helps determine where to initially attack, but I found that I rarely had to stop and look at the cube during the solve. It is like anything where as you become good at it your vision becomes "faster" so you can instantly recognize the next pattern you want to attack and go from one tool sequence to the next. Perhaps with the more complex tools he would be using the inspection is more beneficial. What I was using were very simple sequences of 3-5 moves to do one thing, like flip an edge or rotate three edges, twist or rotate three corners, and so forth. He may be fixing all 8 corners in a single tool to start - inspection would really help there.