I am not an expert, but it my impression that most important towns had a "primary" temple, so it's accurate in a way.

As for temple choice, I usually role-play which temple gets built. It's true that some temples are redundant next to orders, but don't dismiss law and growth bonuses: they can be useful in certain conditions. It should also be noted that temple types affect character traits. For example, the popularis trait necessary for the Marian reforms can be obtained by being a worshipper of Ceres.