I think they're banking on user behavior being as follows: If the correct number is suggested, you get slightly creeped out, but confirm. If the wrong number i

I think they're banking on user behavior being as follows: If the correct number is suggested, you get slightly creeped out, but confirm. If the wrong number is suggested, you get slightly outraged or puzzled, fill in the right number, and confirm. It's sort of a natural A/B test: will people respond better to the correct number, or the wrong number? And they don't even have to control the A/B population, it's just whatever their reverse lookup API returns.