F3G
I can of course see your point about disclosure, but motoring law isn't anything like aviation law.
Your car 3rd party cover is NOT voided by you modifying the engine, or by driving 10x over the alcohol limit, or by having no MOT, or by towing an illegal trailer attached via an illegal towbar. The RTA prevents the insurers walking away from those. Only the fully comp cover gets voided by those things.
Aviation insurance differs from "normal" insurance in other ways; for example you can under insure the value and they will pay out the insured value. Whereas in normal insurance they will scale the payout down by the ratio of the two values. I am not a broker but this is my recollection.
There are many differences between aviation practices and the sort of insurance familiar to Joe Public, and anyone interested is best to phone a real live broker and not ask here.