I once had an ongoing correspondence with the Advertising Standards Agency on the subject of ivreased sound level for commercial breaks. Having Quoted the standard guidance for relative levels they as good as denied that it happened!! I was asked to provide dates times programme details and advert content before they would look in to specific complaints. I think my reply said volumes at high level as I recall!
I recently bought a cheap telly which includes an auto volume reduction switch, specifically for reducing the volume increase during commercial breaks. So the manufactureers and all of us Know it happens, but not those who pretend to have some control of such things.
Another rant over!!