I don’t work with an EK43, but I’ve also just figured it’s for workflow reasons. I usually prefer brighter/fruitier espressos in milk, personally. However, I find that a high TDS is necessary to get an espresso’s unique characteristics to come through the milk.
I don’t have much insight into using the EK43 for milk, but for those of you who do (@lion_head_coffee, @Stan, @Coffeeforkicks), do you find the espresso is too bright or low TDS to pair well with milk? Or does it help the origin cut through the milk?