Ultrasonic fingerprint sensors aren't optical like the older under-screen ones. They don't need to go bright to get a reading.

This will not blind you, it shouldn't boost brightness at all.

*on the power button.

My s10e had this, and it's the best IMO.

You can also swipe it to pull down the notification shade.

The pixel 9 doesn't do the blinding thing anymore, and it works pretty well. This is apparently an even better version of that.

Don't disagree that on the back should be a thing too, the sensor on the back of the pixel 5 (IIRC?) was perfectly quick and had a few useful gestures you could use it for. I doubt it would increase the BOM much to just have both considering we're talking at phones that cost a grand

Like others have already said the 9 doesn't use light/optics but it still sucks compared to the one on the back. I use, but generally dislike the P9 finger print reader. I've gone so far as not using a screen protector to help that stupid thing. Still has way too many error reads