That "don't tell me what I don't want to know" ends with your broker! The underwriter on the other hand doesn't care about what you or he discussed, you will loose in the end!
I have an Excel spread sheet with all my shop purchases, itemizing where and when I bought them, how much they cost at the time and a space for "current" value which every so often I update.
I have no doubt you're correct about that chain of command. I've been around enough to know that the greasy "don't worry, I'll take care of you" handshake from the guy that takes your money, is different than the one when it comes time to dole it out.....I don't want to make sweeping generalizations about professions, but.....
I still do not believe that they have much of a case to not pay out on your claim of a kitchen fire if they discover you also do welding in the garage occasionally. Not saying they wont try, and lawyers wont get richer doing it though. But I have a hard time believing that in most cases a judgment would not eventually be in your favour if the root cause of the fire was verifiable and within the scope of the contract regardless of breachable activities or legal fine print. Most of that fine print stuff in contracts is not actually all that enforceable, but it is a good first defence and deterant. As with most things legal your success might depend on your level of representation. There is case law, and there are bad lawyers, and your defense is only as good as you can afford sometimes.
Annecdote story time (because I just thought about this), My Aunts Neice from the other side lost their house a few years back to a fire pretty close to here. I don't
really know her, or all the details, But I know it was an oily rag that caught fire in the garage due to welding sparks, and the house was a total loss. No idea about the insurance side of things, but there is a brand new house (much bigger and nicer than the one it replaced) sitting on that lot today, and they still live there. They are not rich, just middle working class folks like me, so they're either in debt up to their eyeballs and mortgaged for life from having to foot the entire bill to rebuild, or insurance paid out on the claim, even though it was caused from a welding accident, and poor housekeeping. I kinda forgot about that, and I'm actually curious about more details now, and will press my Aunt next time I talk to her. I don't know them well enough to stop in when I drive by and say "hey, Remember me from when we were kids? we have the same Aunt, you mind telling me all the details about your house fire?"

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I've always loved a good spreadsheet, but part of me doesn't really want to see that =SUM #.....