Not even secure
Without getting as far as privacy, facial ID is not even secure.
If you are simply sending a 2D image, that is well known not to be secure. That security on a phone would not be taken seriously.
If you are sending a 3D image, it is still not secure (never mind surmounting the problem of defining a standard). Once the standard is known, it will be easy to generate fake 3D from 2D pictures Besides just pure guessing at z-coordinates, a few 2D pictures taken from different angles could be used to generate accurate data. And it not like there aren't a zillion selfies on Facebook to work from.
It would be different if you went to an IRS office and were subjected to a live scan - but that wasn't the plan.
The whole idea was born of a smattering of tech keywords and a lot of stupid greed.