As an adjuster I wouldn’t cover this. Your policy only covers damage to your property. You yourself did not have damage. You had a leak to another persons unit, which is wear and tear regardless and not covered (plumbing repairs for the leak).
Tear out is not damage. Access is not damage. The leak must have caused physical damage to your dwelling in order for tear out to be covered. Just because a plumber labels it sudden and accidental doesn’t mean the policy covers it. Floods and earthquakes are also sudden and accidental. Lol
Agents cannot tell you what is and is not covered. They are not licensed to tell you that. They should only be going over your policy with you and telling you to file a claim.
And idk anything about “3rd party”. Plenty of adjusters are independent or contingent because there are no physical adjusters in your area that can inspect. An adjuster made a coverage decision and more than likely didn’t need to visit. Half the time we don’t need to physically visit properties when we see clear denials or things that can be handled view photos. What would the adjuster have seen physically that he could not have seen via reports and photos?
Also DOIs are for making sure the claim was handled properly. They VERY rarely overturn coverage decisions as that’s not their place. They want to make sure the law was followed.