I'm sure they will do a more thorough check if you rear end a more expensive and luxery car or god forbid knock a child down or something.
They will look for anything and use it as a get out claus.
With my Glanza, it was fully loaded, forged, different turbo, everything that could be changed was replaced with aftermarket parts. My modification list was as long as my arm and I declared every single mod..everything.
The company I am with are mod friendly and game me a quote on my BHP..which was 275hp and were happy with all my mods and was on a like for like basis.
There are no excuses.
Personally, I don't know why people buy cars and mod them if they can't afford the extra premium for modifications, but we are all different.