So, there needs to be a benefit, either in taste, quality, or ethically, to make the premium price worthwhile. In using A2 milk in coffee, the benefit comes from the quality of the feed used to produce the milk - A2 milk dairy cows are not exposed to the Silage Season, where the dairy cows are fed fermented grass - this season which is unpredictable to the consumer, which results in another variable that we need to account for. This can be the reason why one day your steamed milk is velvety smooth and creamy, and the next day, with a new bottle of milk, the results a re a bubbly mess with separation in the foam.
If you are chasing a consistently high quality steamed milk, A2 may be the answer. It is also thought that the higher protein count in A2 milk can improve the results too.
If you don't want to select A2 milk, you can instead reach for regular full cream milk (4% fat) instead of light milk (2% fat) - the light milk will almost always result in a fluffy steamed milk which does not have the same mouth feel or texture of full cream milk, or A2 milk.