Casein is a stabilizing agent derived from milk ; it probably doesn’t add taste, but it serves the purpose in making the thing what it is. Bittul b’shishim does not apply. Sorry. As the hechsher correctly states, it’s dairy.
As far as the legal standards, I don’t think the OP was claiming to have a legal complaint. Ethically, is there something wrong with using a dairy product in your food and calling it “non-dairy” because it flies under the legal standards? I personally believe so, but that’s not an argument not to hechsher it.