Except that 'pisteuō' means more nearly "to be faithful to" or, one could even say, to enter a type of contract (thus the Greek construct 'dia pistis', two parties relating "through faithfulness").

Anglo evangelicalism constrained its meaning to something like "intellectual assent", for its own purposes (in my opinion, it made for better sales models) some time in the nineteenth century. And as you essentially point out, intellectual assent is fairly meaningless.