Got any further info about these more advanced methods?

I haven't seen anything beyond the feature distance models. I have seen the models that essentially recreate you entire anatomy in 3D, place it in a database, then use that profile to match to in the future--almost like a 3D match move artist would do for visual effects. Not sure if this is just a proof of concept though.

I wouldn't be surprised if the millimeter wave scanners at airports have been collecting 3D models of us for this database over the last decades.