Was wondering if a hi-res image was maintained in addition to the tiny passport photo — unlikely in your case. Easier for facial recognition. Retinal recognition crossed my mind.
Interestingly no.
Remember passport photos require the right(?) ear visible. MUI there are unique ratios between ear canal, eyes, nose and cheeks that can be used to identify you, even form standard res photos.
My wife looks different from her passport photo (shocking, eh?) and it got her on 1st scan as well.
That may be the frightening part.