In case of a commercial hosts, the insurance for the trip is provided for by the host’s own commercial policy and not by Drive lah. The conditions of the commercial host policy are clearly mentioned on the host’s listing page.
The Drive lah protection insurance policy terms are leading, which means that the commercial insurance needs to cover what Drive lah covers. For example, the excess for a Drive lah trip is $3000, which means that regardless of the excess charged by the commercial insurance, the guest is liable for $3000. Possible higher excess from your own commercial insurance will not be covered during a Drive lah trip.