Bill was taken aback, he clearly didn’t know about this part. Not a surprise; he would have been told about the ceremony up to this point. The part where he proves himself was meant to be genuine and having a surprise like this tends to lend that response. Only other Veela would know what is to come, but that is their culture. Honestly, I would rather not know what I had to do to prove to my lover. Knowing that you had to perform three acts of dedication and prowess would be far more stressful. 