I know what the Pixel 4XL has for facial recognition, I have one and looked at this long before purchasing the phone.
However, it would be very easy to program the Pixel 6 to allow for facial recognition to open a locked phone like the Samsung S21U. I had one of those for a few days before returning, and the facial rec worked quite well.
I was told, but didn't have the phone long enough, that for a secured app such as a bank you had to use the FPS to access that app. I didn't see any notation about that when setting up the facial rec of the phone, since I have no secured apps to access (I will never put a secured app on my phone regardless of the security required to access) never tried the feature. Maybe someone with a S21 can answer that.
But how hard would it be to program a 6 to allow for facial rec to open the phone but require the FPS to open secured apps? Since I am not a programmer I have no idea.
However, all this might be immaterial to me. Even though I keep hoping to get a Pixel 6 I keep swaying further to another phone due to what I keep reading about the Pixel 6. A lot will depend on what happens in the near future with S22 reviews and how google steps up to fix the problems in the 6 series.
If the S21U I had for a few days had been able to update the software (OS), and Samsung could get it to update when linked to the phone I probably would have kept it and just moved on. However, after 45 minutes they told me to return the phone, it has some serious problems. Therefore, it was returned and I am back to where I was a few weeks ago. Wanting a Pixel 6Pro but concerned will it work where I live as a phone.
Until then, the 4XL will suffice.