It seems relevant to the faith vs rationality discussion. For me, rationality strongly implies testability. Unless we're talking about mathematics, and not physical reality.

First of all, if there's a special get out clause for mathematics, why shouldn't there be a special get out clause for God? God isn't part of physical reality either.

But anyway, the question was whether religious belief was necessarily based on "blind faith", not whether it meets some kind of positivist criterion of ideal rationality. People who believe in God wholly or partly on the basis of arguments aren't believing on the basis of blind faith. You might think the arguments are bad, but you could have a rational discussion with them about that.