A call requires a human, which is inherently not scalable. And even humans have trouble distinguishing AI content these days.

And it's not like Discord actually cares. They just care about appearing like they care. Something to keep the heat off of them from regulators and angry parents.

A “video call” perhaps requires a human, but the type of test described need not be a video call. One can imagine a network trained to distinguish a fake id card from real one from a video recorded where the user is asked to move the card such that the holograph is glinting in the sunlight.