That wouldn't surprise me, and I do frequently add vinegar to my almond milk when baking to make it more like a buttermilk, even if the recipe doesn't call for

That wouldn't surprise me, and I do frequently add vinegar to my almond milk when baking to make it more like a buttermilk, even if the recipe doesn't call for it. The additional acidity when adding vinegar to a recipe that uses baking soda or baking powder can replace some of the effect of using sour cream (a very common "secret ingredient" in non-vegan chocolate cakes), which provides more leavening. It probably also alters the flavor in some way, though there are so many other competing and strong flavors, and the vinegar is such a small amount, that it probably doesn't do too much. I don't think I've used vinegar in my chocolate cake attempts, however, so it's probably something I'll try next time.