Flood damages are commonly mishandled during the evaluation phase of an insurance claim. It is not necessarily a case of an adjuster not wanting to approve everything that the owner is entitled to, but, more of a case that the adjuster's forensic skills are inadequate to fully assess all of the damage. Flood water is very unsanitary water, all contaminates from dead animals, oil from cars, sludge ponds on pig farms, fertilizer in storage barns, and the like are absorbed by flood waters.
These contaminates will find there way into a home, including the crawl space, between base plates and the sub-floor, between the sub-floor and the floor joints, and between all joined wall members and headers.
An adjuster's write-up will normally afford the tear out of all sheet rock up to a common joint (usually at 4' above the floor) and afford a wipe of all surfaces by a "technician". Although the intent is notable, the effectiveness of such a scope can be less than complete and can result in a number of "hot spots" that will continue to proliferate, resulting in ongoing fungal growth to a point where the home becomes unsuitable for occupancy.
Prior to accepting a scope from an insurance carrier, consider contacting a 3rd party capable of analyzing the proposal on a forensic level.