For me it works fine in any case. I really wonder if this may have to do with the patterns of fingerprints. Just like some face unlock and photo camera software is biased towards certain ethic features, the fingerprint software may be callibrated better for a certain swirl in fingerprints.
I have an ulnar loops fingerprint on my index finger and a double loops on my thumb (mostly use this one). Both work fine for me. What about those who have issues?