If you can really truly get a consistent texture that yields "pourable microfoam" (the type of foamed milk that yields great results for latte art), it's not easy to just vary the amount of foamed milk vs fluffy foam.
In our shop and due to local preferences we stretch the milk to 80 degrees for lattes before plunging the steam tip and stretch it to 100 degrees for cappas in order to get more foam or a lighter fluffier layer of foam. When a customer request a latte with "no foam or very little foam" we can control the amount of foam going into the cup byt holding a flat bladed spatula knife across the pouring spout edge of the pitcher. When they request their cappa "wet" we release just a bit more foam at the end of the pour. When they request it "dry" we don't hold back any foam at all.
I'm in agreement that an ideal ratio is 1/3 to 1/3 to 1/3 but we also need to accomodate hte desires of our customers or they will go elsewhere. That's not to say that we can't educate them and we often do. If I sense that a customer is open minded I often suggest going with a smaller cup size and getting a quad shot (our standard shot for all drinks is a 1.5 oz double ristretto). They are typically surprised by how good the drink tastes - usually because they asspciate espresso with the bitter taste and burnt taste of Starbucks.
And an espresso with whipped cream is an "espresso con panna".