Maybe because the index finger is smaller the scanner can see the whole thing better than our fat thumbs and has a better result?
It would be interesting to see if most of you having problems are using thumbs and if those of us that have it working perfectly are using a finger.
I've had a couple of issues with the fingerprint scanner not reading my thumb a few times and it was a little frustrating until I heard I think on a podcast or youtube video I forget (I've watched so many over the past week on the Pixel 6 line) and I heard about this tip on the Fingerprint setup, You can setup multiple fingerprints but instead set up the same finger multiple times, I set up the same thumb twice and the same Index finger twice and I haven't had issues since. It's a good tip.
Compared to my year old S20 FE 5G the P6 fingerprint sensor is subpar. My S20 is much faster. Disappointing to see what Google rolled out. Still debating on whether to move to P6 or keep my S20.
Try to register the prints after you've moisturized your hands a little bit. Maybe it will help. I'm not saying definitely, but it's worth the shot since it seems like you've tried a few times..My scanner has yet to improve. Registered my prints over and over but still no good. Hope it improves.
I've had the pro for 2 days and registered four fingers, and as you said was very careful to really cover all angles, with the most prominent parts multiple times. For my things I trained the scanner in the way I'd be holding the phone when I'd be unlocking with the thumbs, ditto with the index fingers.I initially had some issues with the fingerprints but I re-did the scans and made sure to move my finger around A LOT when registering the thing. Seems to work a lot better now, I just have to remember to hold my finger down a second longer than I think I should.