No tea latte at Kyōyo Haus is built from scratch when you order it. Every one of them is pulled from a concentrate that was made earlier that day or earlier that week.
The batched matcha is 31 grams of Kagoshima ceremonial matcha into 250 grams of hot water. The batched hojicha is 28 grams of hojicha powder into the same 250 grams. A latte takes 40 grams of one of those, then 180 grams of milk and 20 grams of simple syrup. The whisking happened once, into a batch, rather than once a cup with somebody waiting at the register.
Speed is the smaller half of the reason. Matcha whisked to order into a fourteen ounce cup of cold milk does not actually dissolve. It clumps, and then it settles to the bottom while you walk. Hot water first, in quantity, is what gets the powder fully into suspension. Making it ahead is how the tea ends up in the drink instead of in the last inch of it.
Simple syrup is the plainest thing on the shelf and follows the same logic: 250 grams of turbinado into 250 grams of hot water, one to one. Sugar does not dissolve in a cold drink either.
Ube and pandan share one frame. Both start with 40 grams of turbinado, 120 grams of hot water and a pinch of salt, and then split: 12.5 grams of ube extract with 50 grams of condensed milk, or 8 grams of pandan extract with 45 grams. Forty grams of the finished concentrate goes into each cup.
That frame is why those two are the only lattes an oat milk swap will not make dairy free. In every other drink the milk is poured at the counter, so leaving it out is a decision somebody can make while you watch. In these two the condensed milk is inside the concentrate, cooked into the batch long before your order existed. Ask for oat milk in an Ube Latte and you get oat milk, along with the condensed milk that was already in the jar.
Black sesame is the one with no dairy in it anywhere: 210 grams of black sesame paste, 58 grams of turbinado, 11 grams of sesame oil, 222 grams of hot water. The paste and the oil carry the whole flavor, which is why it takes the same 40 gram pull as the tea concentrates.
If you want a latte without dairy, order matcha, hojicha or black sesame and ask for oat. If you want ube or pandan, order them knowing the milk is already in the jar.