My understanding is that the GOS developers only considered the Pixel 4's facial recognition hardware to be secure enough. The pixel 4's hardware included a dot projector and a infrared emitters and it basically made a 3D image of your face to use as a password. After pixel 4, google stopped using that much more secure technology, most likely (according to AI) because all those extra sensors took up a lot of space at the top of the phone. The way google currently does it on the pixel 9 is basically taking a 2D image and uses software-based AI processing, which sounds a lot less secure to me.
Supposedly the way Apple Face ID works is an upgraded version of the Pixel 4's system (it uses more 3D points to create the password), except Apple spent Billion's of dollars in R&D to figure out how to miniaturize the hardware to fit it all in the top of the phone. I'm not an apple fan boy any more, but it sounds like they may have android beat in the facial ID arena.