It says any "randomized" hits...Gosh.
Hits from models in BtB contact were never randomized...Except for impact hits.
Hydras aren't CC attack magnets.
War Hydra, Special Rules
Change the Beastmasters special rule to “Beastmasters: The bulk of the War Hydra makes a great shield for the Beastmasters that drive it, protecting them from missile fire and close combat attacks. Wounds that would normally be randomised between the War Hydra and its handlers are instead all applied against the War Hydra.”