King of the Hill map island version

When playing King of the Hill in random map mode vs ai it randomly selects between 3 versions:

Island map with the plenty vault on an island surrounded by ocean

Snow map with the plenty vault surrounded by ice

Grass map with the plenty vault partially surrounded by cliffs

But on online games it never seems to be the island version. Only one of the other 2. Does anyone know why this is? And is there a way to choose which one it will spawn?