Insurance lowering material cost below Xactimate price list

Exactly. In Florida codes are enforced and inspected.

State Farm Fire and Casualty Company v. Metropolitan Dade County was a 1994 decision in Florida. Florida enforces codes across the entire state so its a moot point. In this case, the policy in question is a seldom used Special Form 3 and Extra Form 5, which contains the following pertinent provisions: The “Ordinance or Law” clause provides that State Farm is not responsible for loss caused by the enforcement of ordinances or laws regulating home construction; the “increased cost limitation” clause excludes from coverage any increased costs of repairs which are incurred by bringing a home into compliance with ordinances. The trial court ruled the policy verbiage was ambiguous. This was later reversed and judgement awarded in favor of State Farm.

The HO 3 policy which most people have these days also has this exclusion, but there is a common endorsement which then provides coverage.
"Building Additions and Alterations for the increased costs you incur due to the enforcement of any ordinance or law which requires
(1) The construction, demolition, remodeling, renovation or repair of that part of a covered building or other structure damaged by a PERIL INSURED AGAINST

In terms of manufacturers requirements, the policy doesn’t insure warranties. Different manufacturers have different requirements so the average adjuster wont even consider that. The IRC IBC doesn’t define “solidly sheathed decking” if the argument is “we must redeck the house due to IRC/IBC because there is an 1/8th inch gap on plank decking”

To go even further-nailable surface isn’t covered either unless the decking is damaged by a covered loss. This comes up often when the decking has deteriorated due to long term seepage/wear and tear and leaves rotted wood, soft decking etc. Its already otherwise excluded on the policy.