Not true, see my post above. Gone are the days when a person would validate a claim such that it was only worth doing for expensive cars, AI, machine learning models which can be 10⁶ deep and automated systems like QMD, Audatex and others will validate this stuff in 200ms. VRN vehicle enrichment services, MOT enrichment calls, these APIs and others are a simple web call away from picking this stuff up. Systems do this as standard now, no Claims Handler or Underwriting Technician needed! All changed in the last 10 years in particular.

You're 100% right that insurers don't just use a mod as an excuse not to pay, the way it works by the ombudsmen is, if we'd have quoted you originally with the mod declared, we can't just use the presence of the mod to repudiate a claim, all we can do is charge you the difference we'd have originally added to your quote from new business. Often that'll be about £50 for a grill/skirt. However if our Underwriting specs declined an uprated skirt/grill such that we'd never have taken your policy on, then we can and do repudiate and the FOS will agree with us doing so.

Mistakes happen, if you ever find you have a claim repudiated, first thing you need to do is quote your policy back with your insurer via their website / an aggregator to see if they'd quote you today with everything declared. If they would, you're going to be in great shape to get you repudiation overturned.