Cow’s Milk—Without Cows
The usage of the term "yeast spitting out milk proteins" is by the founder of "Perfect Day".
Perumal Gandhi and Ryan Pandya are the co-founders of a startup company named "Perfect Day" in San Francisco.
Ref. fortune.com.
They got a strain of yeast, which they call Buttercup, from the U.S. Department of Agriculture. The yeast ferments sugar to make real milk proteins (casein and whey), which are then combined with plant-based fats and nutrients to get milk that’s lactose free. https://fortune.com/2016/08/31/animal-free-cows-milk-perfect-day/
The founder of "Perfect day", who is trained in biomedical engineering used a informal term "yeast spitting" for this process, which is technically known as "yeast secretion". He
He also highlighted the fact that they are slaughtering trillions of yeast cells (no animal slaughter). Google search would show the term "yeast spitting" in some locations. Similar process for making beer from hops; wine from grapes; penicillin made from penicillium; etc.