It’s a no win situation to address this. There were no witnesses so it is a he said vs he said story. Any attempt by William to address H’s recounting of this alleged altercation would merely lend credence to H’s tale.
There's many ways addressing it could go but I just don't see how they can totally ignore such an accusation. And to be honest I would think worse of them if they did not address it... I'd say the same for any celebrity who is accused of assault, sexual assault, or another violent act by the alleged victim in such a public way. If it's totally untrue, at least confirm for people it's totally untrue and explain what happened in your perspective.