If they offered a significant transfer bonus to Hyatt, wouldn’t they “suffer” an immediate and massive outflow of cash to pay for those points as presumably everyone would drain their Bilt account? I just don’t see that happening.

While 100% to Flying Blue is probably quite nice for those who are familiar with FB, I suspect that the vast majority of Bilt customers has never redeemed a FB award and thus might not jump on it. And 100% to IHG is, uh, still resulting in IHG points.