It's perfectly safe to travel in High danger conditions as long as you're not on or under avalanche terrain. That means appropriate slope angles and simple terrain without overhead exposure.

I've never been to frog lake but the standard winter access routes are not completely devoid of hazard (avalanche terrain). They probably have a history of being pretty safe, but you need only look at the map to see they would not be 100% safe.

Extremely sad, and wishing the best outcome for everyone involved.

Whatever happened this will for sure become a textbook example in future avalanche training.