Fact is the majority of the Insurance companies do not have a clue what an uprev is and resort to the question about power increase, which less face it is why the majority of us have it done.
Would they know if you didn't say you had one done? Maybe not, but as they ill do their best to avoid payments and they do find out it that it hasn't been declared following a claim that is your insurance voided, something I would not want with the subsequent consequences.
Someone I know is employed in an insurance company to check this stuff and that includes what they find on public internet forums....so not declaring it is stupid, IMO.