Why does the merseen_twister_engine guarantee certain results?

I note the following on cppreference's article for std::mersenne_twister_engine (e.g. std::mt19937):

The 10000th consecutive invocation of a default-constructed std::mt19937 is required to produce the value 4123659995.

The 10000th consecutive invocation of a default-constructed std::mt19937_64 is required to produce the value 9981545732273789042.

Assuming that this interpretation of the standard is accurate, what's the deal? Why do these guarantees exist? Isn't this non-random?