They are creating a credit score for you. They’re asking for the essentially the same data a credit scoring agency would use. The difference is that they manually underwrite everything.
Spain also enforces a much stricter debt to income ratio, which means it’s much harder to get loans for people that already have debt, which means the risk profile is reduced for those that do get approved.
Also Spain’s unemployment is among the highest in the EU — and almost three times higher than the U.S., so the central bank’s lower interest rates reflect less of a concern over inflation and more of a concern towards encouraging growth. The low interest rates in Spain aren’t a reflection of reduced risk but of lower central bank rates. You could get 30 year mortgages in the U.S. just a few years ago approaching 2%.
Comparing mortgage rates across countries is a pointless endeavor because the macroeconomic circumstances are vastly different. For example, one would think that lower interest rates would result in a increase of housing supply in Spain as investors build more housing because the loans would be cheaper — however that isn’t the case because of the post-tax return on investment (and regulatory risk) for real estate is far worse than an equivalent investment in the United States despite higher lending costs. A €10 million housing project in Spain has a lower ROI than the same project would in North Carolina. Interest rates could be zero in Spain and it wouldn’t change the housing market much because of the myriad of other factors that go into the spreadsheet.