Atlas. Chance of a certain type of ultimatum appearing.

In my atlas tree, the appearance of the ultimatum with "defeat waves of enemies" is improved. But in reality (on 25 maps) I have "protect the altar" in about 80% of cases, is this normal?
To check, I improved the appearance of all three other versions of the ultimatum, but on 6 maps in a row there was "protect the altar", what is this?????