I know of a certain large insurance company that still pays out (albeit less than they could potentially) if mods haven't been declared. I'm by no means stating not to bother, at the end of the day it's up to the individual. I have my mods declared, so i'm not bothered either way, it's just an observation through experience with assessors. Get off your high horse
Are you seriously saying that if a car "looks" standard that an assessor would plug into an ECU and know what the map codes are etc? More to the point would they remove the inlet mani and know it had been ported? or know that cams we're standard. They just don't have the time to do these things.
You can appreciate peoples reluctance to not covering mods as most insurance companies won't cover the mods themselves, so if you do crash, you would get a standard car back, or money depending on the claim/car value.