Stone, do you realize that there is no proof at all in that video?
First, as many said, your game experience actually makes you think there are something like 5k players. So, why would a guy spend so much time in order to proof there is a scam? Only someone that WANT to arm Nostalrius reputation would do so.
From that point, how can you trust the figures he will display in his video are true? If you don't actually do the test yourself, and review his code yourself, there is no point in linking the video as a proof.
Then, and more seriously, let's examine his "method".
He wants to show that there is a difference when you:
1) sum up the result of /who in the area for each level.
2) scan players 100y around 11 of his toons.
Then, he says that 1) gave ~500 and 2) gave ~250. Thus it is the proof that 1) is a fake from Nostalrius.
Let's examine 2)
Like he said himself in his descriptions, he used 11 characters, covering 100y radius areas. How the fuck can you cover 100% of an area with 11 characters? 100y is not as much as it seems, go and try in game by comparing to your 30y spell range. His method only allows him to cover something like 20% of the area. Assuming he covers most frequented zones, there really is nothing surprising he still missed 40-50% of the players.
He shows were his characters are, on the map, and you clearly see that, except 2 first characters, they are more spaced than ~200 yards. Go ingame, use your 30y spell range as unit, and you will see it yourself!
About 1)
He affirms 1) is fake.
It would mean that is you /who players in a zone, at a given level, half of them don't exist.
The point is, when I look for people for a dungeon, I generally use this method to wisp players one after another. I did this on many servers and on retail. There is a part of people who will never answer back, because they are afk, or beacause they don't speak english (especilly on eng private servers).
Thus, if half of players are fake, you will never get an answer from ~75% of them!
It is so easy to try it on Nostalrius that I actually did it!
I was in darkshore and selected all players at level 15. There were 11 results. I wrote them all, and after 2 trials, 9 out of 11 answered me. One disconnected in the meantime. The last one did not answered.
Here is the screen shot in attachment.
Happy now?