Playing Heroes of Might and Magic V on Ubisoft servers.

That's exactly what I'm saying.
The tests were definitely done on the first difficulty level.

So, it's impossible to reach level 17 by day 10.
Especially on the second difficulty level.

There are still skilled players in Russia...

What do you mean by "first level" and "second level"?
Be more specific.
I only know these difficulty levels:
Recruit
Warrior
Veteran
Hero

The tests were conducted on "Veteran". They were conducted before the "Tribes of the East" appeared. That is, the "Path of War" perk was not yet available. With it, the result would be 2-3 levels higher. Any other questions? On the "Ring Road" map (slightly modified for the same test in 3.0), Leto reached level 27 in 14 days. So, your categorical statements about the impossibility of reaching a high level in the early stages are absurd.