The statement says

"The number of intermediate levels of employees between an arbitrary employee who has subordinates (an ordinary employee) and the employee who has no superiors (the main superior) is the same for all ordinary employees."

However, in the first paragraph, it says that "ordinary employee" means an employee who has NO subordinates. Therefore, I think the statement should say:

"The number of intermediate levels of employees between an arbitrary employee who has NO subordinates (an ordinary employee) and the employee who has no superiors (the main superior) is the same for all ordinary employees."

I looked at the Russian version of the statement with google translate and that seems to be the case.

There is also no mention in the statement that the structure is that of a SINGLE tree (and not a forest), but the answer seems to assume this.
The statement only says that each employee has "not more than one direct superior", therefore one can understand that it is possible, for example, that no employee has a direct superior (and therefore the structure is a forest of single-node trees).