He's saying sniping a 500ms gap and a 2ms gap for an experienced player is the same, they know what they're doing so it's not hard.
He has not mentioned whether he thinks it applies the same to newbs, although basic deduction can tell us that no, he doesn't think this.
Is that what you wanted to know?
It doesn't apply to anyone.
The logic he used does, but he exaggerated it.
15 ms gap (the total gap between first and 4th noble if each noble is 5 ms after the last one) on average takes 133 tries to split, and even then has the potential for lag to make the troops return the wrong second (this is why people usually aim to cancel/split i several smaller chunks as opposed to one big chunk, and/or split every gap instead of 1 gap).
While you can do it fairly consistently if you know what you're doing it's not necessarily a 100% sure thing even when facing one train if your internet connection isn't absolutely amazing, and it becomes a total nightmare when facing multiple trains landing at the same time on multiple villages with anything but the best of connections.
A 20 ms gap on the other hand is childs play and is no harder than a 500 ms gap so he had the right premise, he just exaggerated too much. Instead of 133 tries needed to split the 5 ms gap train you only are likely to need 33 tries to split the 20 ms gap train. That's much easier and gives a lot more leeway since even if you set up one chunk of troops to split each gap it's only likely to take a combined total of 200 or so tries. (33 to hit the first split, 66 for the second, 99 for the remaining one)